Formula to substract a range of time from a range of time

Hi Jete,

Once i add more data rows below for eg. b39 and C39, the on production still shows zero while off production shows the whole duration hours. Attached is the file.

The problem that i seem to be having is, when i add more data rows, i can extend the formula in the adjacent cells i.e. columns C,D,E,F which is working. But for the formula columns which currently are ending on column EC, if i add another data row that formula should get extended to ED,EF,EG accordingly and i can get the formula extended in the column vertically but it shows blank after EC.