If you collapse a form so that '.Range' appears in column A, the numeric columns for standard formulas will contain the total across all the range of accounts. In your example, that would be row 51. If you want to show this same total amount when the form is expanded, it is appropriate to have the simple formula =D51; you don't have to use SUM.

If you want to sum a number of different .Range rows into a single amount, you could use either =D51 + D56 + D62 or something like =SUM(D51, D56, D62). Either work the same way.