Okay...So BAD NEWS!
You can NOT do what you want with the way your current Excel file is configured.
Because you cant select a cell for a formula, if the SAME cell is going to be BOTH the INPUT value AND the OUTPUT value.
It creats a loop that infinitely subtracts .7......basically an ERROR.
YOu MUST FIRST copy all the values from the current cells that need a .7 subtraction, and place them in a different cell that you can use as an input value.
So.....basically make a NEW column for OLD values....and have that be WHERE the values go.
Then you can make the formula subtract, and put the output (product) into the column you are using now (15 day)
The OLD VALUE column can be hidden, keeping your format the same.
Does that make sense?
I can do this to your file, and send it back to you with the First Block (FHA 30) completed, so you can see how it was done....YES?