IRA limit on the Worksheet called Social Security recipients who contribute to a traditional IRA line 2

Taxpayer is on social security and is also a minister with a church.  He has a wage in box 1 of the W-2, schedule C income and some excess housing allowance that is reported with the wages on the form 1040.  I added the wage from the W-2, plus the schedule C net income less half the FICA tax on the schedule C income.  I expected to find this number on the Worksheet called Social Security recipients who contribute to a traditional IRA line 2. 

The number on line 2 is much lower and is restricting the IRA contribution. 

Do you know how I can see the math the program is using to get to wages and other earned income on line 2 of this worksheet?  I am afraid the software knows a special rule for clergy that I don’t know.  I was going to just override the calculation but hope to first see the math

Any ideas?