I am an electrician, renovating an office/warehouse. There are 2 area measurements on the drawings. 1 is 'area of renovation' 9650 RSF. The other is 'office/support area calaulation' 4100 USF. Which do I use to calculate general lighting load?

What exaclty is it you want to calculate? Are you looking to determing how much lighting to use or what the proposed lighting will draw in current? Both are straight forward if you have some of the specs.

I'm doing a service load calculation. I know there are several other factors involved but this one will make a pretty big difference in sizing the service.

You will need to figure on the entire building the service will handle.

I note that the area of reno is "RSF", and the other area is labeled "USF".

You may need to call the person the drew the plans to learn what these abbreviations mean.