Why is the total on Line 437 different than the total of income tax deducted according to T4A, T4A(OAS), and T4A(P). It was Less by1038.73

I added the total tax deducted of T4A, T4A(OAS) and T4A(P) manually  and they add up for me as a lot more than turbo tax included on line 437.  Can you tell me why?