Form 1040 line 4b taxable IRA distribution appears to be grossly incorrect

Total IRA distributions line 4a is $37103, comprised of 4 different distributions, and is correct.  Taxable amount on 4b shows $4811.  The taxable amount should only a few hundred dollars less than the total amount.  

 

I went through the 1099R's for the 4 and see nothing wrong.  All are normal distribution code 7 with IRA box checked. Though there should be no connection, the total tax withheld for the 4 1099R's is $4809 (kind of close to the $4811).

 

I don't see any way to determine how TT came up with $4811.  Clicking on the number in the 1040 form and using the magnifying glass just shows me  all of my 1099R's.