Standard Deduction Married Senior Calculation

I am married and over the age of 65.  While my standard deduction is calculated correctly I cannot find a worksheet that calculates the standard deduction.   The deduction on my 1040 reflects the standard deduction plus the additional amount for a married senior - $24,800 plus $1,300 = $26,100.   What I can't find is a worksheet that calculates the the $26,100.  

 

As an experiment, I did change my year of birth on my personal information worksheet to 1980 to see if it eliminated the senior deduction.  It did. 

 

Wondering if there is a worksheet that does show the calculation for the $26,100?

 

Thanks