The columns are as follows:

 - Timer Id: This gives the name of the block of code being executed    
 - Time: The time it took to complete in seconds 
 - Avg: The average time it took to complete in seconds 
 - Cnt: Short for Count. This represents the number of times this individual block ran to generate the output required 
 - Emalloc: The amount of memory PHP ( the programming language on which Magento runs) assigned to this single operation. This is again represented in bytes. 
 - RealMem: The actual amount of memory used to perform the operation.