You haven't provided very much information here. The formula is doing what you told it to do..

=OFFSET (C$... start in cell C4 - which contains AM)
,, (stay in the same row)
C2-1 (subtract 1 from the cvalue in C2 - 2 - which gives 1 and move that number of columns to the right of your startng point. That gives you E: the contents of D4, one row to the right of your starting point.

What did you want as the answer... and why?