I am trying to amend my 2017 MO state tax as a result of amending my federal tax due to ESPP sale of stock. I am using a fillable calculating copy.

On line 43 of MO-1040, it asks me the amount paid on the original return. Does this mean line 42 of the original MO-1040?

What are lines 44 and 45? When to add on line 45 and when to subtract? I am not sure how it is calculating the value on line 45 but I can't seem to modify it?

The fillable calculating copy works fine if I don't fill lines 43-45 and simply correct the Federal adjusted gross income on line 1 (from the 1040 X) and tax on line 13 but I don't think that's the right way of doing it.

Please advise.