@Belzelbub
Gas pressure is the blue line, superimposed on the dive profile. Gas use ends on surfacing, yes that is what is used in the SAC and RMV calculations, 1920 psi in my example (start gas pressure - end gas pressure).
The dive itself does not end until 10 min after surfacing. If you descend again, within that time, it will be counted as a singe dive, rather than 2 dives.
Edit: @EFX was posting at the same time I was. My Shearwater Teric captures the same start and end pressure that my Oceanic VT3 does. Calculation of the SAC is identical. Shearwater does not automatically calculate RMV, as cylinder characteristics are not captured. RMV is calculated from SAC by multiplying by the tank factor (vol/pressure, cu ft/psi for imperial)
My VT3 has a default end dive time of 10 min. My Teric is adjustable, between 10 seconds and 10 min, I have it set at 10 min to match the Oceanic. You can end the dive earlier with a button push when a prompt comes up on the screen. I don't think I've ever found this in the owner's manual, but it is intuitively obvious.