I was training at a school that had two hour meters installed in each helo (S-300).
One meter clocked time from master on, the other from collective up I suppose.
The charge was for master on time. The other clock for maintenance.
A typical flight took about 2 min for prestart, 4 min warmup, 10 min flight to practice area and 10 min back and another 4 min cool down. That leaves about 30 minutes from each hour lesson for actual training. Needless to say, I have abandoned that school.