The Text Appears with the dropdown on Custom Module

Question

My code on a custom delivery time module works all fine but it shows the given text outside the dropdown box , I racked my brain trying to fix this and I still couldn't , please do help!!

WorkingOff.php

<?php
 namespace Shl\DeliveryTime\Block;
 use Exception;
 use Magento\Backend\Block\Template\Context;
 use Magento\Config\Block\System\Config\Form\Field\FieldArray\AbstractFieldArray;
 use Magento\Framework\Data\Form\Element\Factory;
 use Shl\DeliveryTime\Helper\Data;
 use Shl\DeliveryTime\Model\Api\Data\DeliveryTime;

 class WorkingOff extends AbstractFieldArray
 {   
protected $_template = 'Shl_DeliveryTime::system/config/form/field/working-off.phtml';
protected $elementFactory;
public $_tslotList;

public function __construct(
    Context $context,
    Factory $elementFactory,
    array $data = []
) {
    $this->elementFactory = $elementFactory;

    parent::__construct($context, $data);
}

/**
 * Initialise form fields
 *
 * @return void
 */
public function _construct()
{
    $this->addColumn('working_off', [
        'label' => __('Day'),
        'size' => __('40'),]);
    $this->addColumn('tslot1', [
                'label' => __('Time Slot'),
                'size' => __('40'),
                'renderer' => $this->getTslotList(),
                ]);

    $this->_addAfter = false;

    parent::_construct();
}

public function getTslotList()
{   
    $db =$this->db1('core_config_data');
    $sql = "SELECT value FROM core_config_data where path='mpdeliverytime/general/delivery_time'";
    $result = ($db['connection']->fetchAll($sql));
    if (empty($result)) {
 
        }
        else{
    $base = json_decode($result[0]['value'],true);
    $output = array_chunk($base,1);       
    $from = array();
    $bri = array();


    foreach ($output as $key => $value) {    
    //$from[] = $value ['0'];
    //foreach ($from as $key => $value) {
        //for($i=0;$i<=3; $i++){
    $timeArray[] = $value['0']['from']['0'].":".$value['0']['from']['1']."-".$value['0']['to']['0'].":".$value['0']['to']['1'] ;              
    }
}
}

public  function db1($tbl_name){

    $objectManager = \Magento\Framework\App\ObjectManager::getInstance(); // Instance of object manager
    $resource = $objectManager->get('Magento\Framework\App\ResourceConnection');
    $connection = $resource->getConnection();
    $tableName = $resource->getTableName($tbl_name);
    return $db = [
        'connection' => $connection,
        'tableName' => $tableName,
    ];
}
  

/**
 * Render array cell for prototypeJS template
 *
 * @param string $columnName
 *
 * @return mixed|string
 * @throws Exception
 */
public function renderCellTemplate($columnName)
{   
    if (!empty($this->_columns[$columnName]) && in_array($columnName, ['working_off', 'tslot1'])) {
        switch ($columnName) {
            case 'working_off':
                $element = $this->elementFactory->create('select');
                $element->setForm($this->getForm())
                    ->setName($this->_getCellInputElementName($columnName))
                    ->setHtmlId($this->_getCellInputElementId('<%- _id %>', $columnName));
                return str_replace("\n", "<option value=Sunday>Sunday</option><option value=Monday>Monday</option><option value=Tuesday>Tuesday</option><option value=Wednesday>Wednesday</option><option value=Thursday>Thursday</option><option value=Friday>Friday</option><option value=Saturday>Saturday</option>", $element->getElementHtml());

            case 'tslot1':
                
                $db =$this->db1('core_config_data');
                $sql = "SELECT value FROM core_config_data where path='mpdeliverytime/general/delivery_time'";
                $result = ($db['connection']->fetchAll($sql));
                if (empty($result)) {
                    $count=1;
                    $timeArray[]=0;
                    $newstring="";
                }
                else{
                $base = json_decode($result[0]['value'],true);
                $output = array_chunk($base,1);       
                $from = array();
                $option[] = array();
                $c = array();     
                $count = 0;
                $newstring="";        
               

                foreach ($output as $key => $value) {   
                //$c = $value[$key];
                
                $timeArray[] = $value['0']['from']['0'].":".$value['0']['from']['1']."-".$value['0']['to']['0'].":".$value['0']['to']['1'] ; 
                $option[] = "<option value=$timeArray[$key]>$timeArray[$key]</option>";


                $count++;          
                }
            }
                 $element = $this->elementFactory->create('select');
                               
               
                $element->setForm($this->getForm())
                        ->setName($this->_getCellInputElementName($columnName))
                        ->setHtmlId($this->_getCellInputElementId('<%- _id %>', $columnName));

                for($i = 0; $i < $count; $i++) {
                $newstring .= "<option value=$timeArray[$i]>$timeArray[$i]</option>";}                                            
                
                return str_replace("\n", $newstring , $element->getElementHtml());
                break;
            default:
                break;
        }
    }

    return parent::renderCellTemplate($columnName);
}

/**
 * @return string
 */
// public function getAddButtonLabel()
// {
//     return $this->_addButtonLabel;
// }
}?>