Well, people gave you the answer, but didn't teach you to fish . . .
The tank you were using was a steel 117. The working pressure on that tank is 3442 psi -- that means that, to have 117 cf in the tank, you need to have it filled to the +10% pressure, or 3786 psi.
So, if you have 117 cf with 3786 psi, that means you have .0309 cf per psi (or, as a little easier number to work with, every 100 psi in the tank represents 3 cubic feet of gas). So, you used 2300 psi out of your tank, which is just about 69 cubic feet of gas.
The important things to know (because you can do these calculations for any tank) are the capacity of the tank, and at WHAT pressure that tank holds that much gas. This is important, because some tanks hold that volume at the service pressure, and others only hold it at the +10% pressure. And some tanks aren't ever filled to plus ten, so, for example, an Al80 is 77 cf at 3000 psi, which is pretty much the most pressure anybody ever puts in them.
But once you know the capacity and pressure, you can calculate the number of cf per 100 psi, which some of us call the "tank factor" for the tank. That makes figuring out how much gas you have used at the end of a dive very easy -- just figure out how many hundreds of psi you used, and multiple times a simple digit. If you do the math, the tank factor for an Al80 is approximately 2.5; that means that 69 cf would represent 2760 psi out of your tank -- not a safe dive to do!
Now, go fishing!
