I want to use the sumif function to calculate my total profit for each month.
For example: I have a column titled "month" which I enter in the month I
earned the profit. Then I have rows for each item. In each row, I have an
"earned gross margin" cell which is the total revenue (what I billed the
customer) minus the total pay column (what I paid for it, which is a
combination of summed cells).

When i try to do a sumif as: =SUMF(AG2:AG1999, "Sept", AD2:AD1999) - it
only comes up with $40.90 and it should be $8395.87.

AG2: AG1999 is the column that I have the month in, in this case only "Sept".
AD2:AD19999 is the earned gross margin column, with each cell for example
row 2: =sum(AC2-W2), with AC2 the total revenue & W2 as the total pay.

What am i doing wrong?