Yes I think @RobertB4444 is correct. If you are watching the refund meter change as you enter your deductions, you are probably seeing the difference between the standard deduction before entering the mortgage interest and then it switches to the itemized deduction amount when it is just slightly above the standard amount. This would give the appearance of a little deduction for mortgage interest. Then, with your itemized deductions already above the standard, you see the full effect of adding the charitable deduction.
As a side note, Turbo Tax is no longer adding the balances together for refinances. They seem to have fixed this by not including the balance of the refinanced loan at all in determining the mortgage limitation.
