how do you correct line 5b in 1040-SR if it does not reflect the correct amount from multiple 1099R's line 2a?

[SteamTrain]

@wagilmore 

IF you have some 1099-R forms from pensions, or 401ks, 403bs, 457 accounts (but Not for IRAs) , where box 2a was somewhat lower that box 1 , due to after tax contributions  ( But Not if box 2a is blank, or marked "undetermined"

See the following post:

Solved: Re: 1099-R Pension Income Box1 & 2a not the same

[wagilmore]

i had to delete the 1099R one at a time until I found the one that was added in correctly.  Then I added that 1099R back in and\ line 5b on the 1040SR was correct.