Listen I know these are a little confusing to put down in words. Use multiplication instead of adding the same item over and. Get the Excel file here.
Lets start with the facts.
The Excel FLOORMATH function will round a number down to the nearest integer or given multiple of significance. Listen I know these are a little confusing to put down in words. An easier way to calculate this is by typing 830 AM in a cell then changing the format to Number. Addition and subtraction are calculated last.