ProSeries expert could not help me today.  I was referred to read to this message thread but this refers to 1120S and not 1120 for which I was seeking help.  My problem on 1120:

On 1120 (not 1120S) when I enter Employee retention reduction amount under Salaries and Wages line 13G then amount flows and automatically gets populated on Schedule M-1-Line 5 with description as "Employment credits wage reduction", however, now it gives me error on M-1 as line 10 of M-1 does not match with 1120-Line 28.

My total income on M-1 Line 7 on this return matches but with the above error.  If I also add the same amount on M-1 Line 7 then error goes away but then it does not match with my books.

It seems that ProSeries is not populating amount from 1120 to M-1 correctly or I am missing something.