Tried this with a practice client with social security income in ProSeries Professional.

By entering the above the line $300 deduction, ProSeries is changing the amount of social security that is taxable.  Why?

Didn't make sense to me, so I tried it in another software, and they make no adjustment to "total income" (line 9 of 1040) when $300 above the line charitable deduction is entered.  That other software behaves as I would expect - it modifies the AGI (but not total income) line.

HELP!!!!