Here is what happened. I opened the
workbook & opened the Microsoft Visual Basic window (Alt + F11). In
the Project – VBAProject window on the left I added a module. In
this Module window, I entered the code as you had written. Under the
Run tab, I selected Run Sub/UserForm. I went back to the Generation
sheet & had entries in the C column but they were not correct.
I do not know if this affects it or not but this is what I think may
have affected the process. In the F column of the daily  Readings
sheet is the following formula =IF(E9=0,0,E9-D9)*100 This takes the
present reading, subtracts the previous reading & multiplies it by a
constant giving me a daily total. If nothing is entered in the E9
cell it returns a 0. After entering the code, cell C11 on the
Generation sheet  show 100. When I click on that cell I get the
following formula, =IF(B11=0,0,B11-A11)*100 It looks to me like it
is taking the day  of the month  from B11 seeing it is not equal to 0,
then taking B11 (First Day Of Month) – A11 (Blank) & multiplying
by
100. On day # 2 I show 200, each day increases by 100. Is it
because of the formula entered in the Daily Reading sheet I am
trying to copy  from that I end up with this? Any suggestions which
may clear it up?