Total column

0.5
0.0
2.0
0.0
0.0
0.0
0.0
0.0
0.5
0.5
2.0
2.0

I get 7.5 plugging your data into my spreadsheet.

Previous months are not cleared.

I suspect the difference is rounding. In the formulas that calculate the totals, try rounding the result to the number of decimal places desired. Then the numbers displayed will match the numbers in the computation. Otherwise there might be extra "invisible" trailing digits in the totals column.