Doesn't the time run for 50 minutes (or whatever the set amount is) regardless of the clock's time?
I mean - if the therapist opens the door when the clock says 3:05 - would not still go to 3:55? (on a 50 min hour)
I use the woman's clock - I walk in at X:01 and walk out at X:50. If the woman's clock was set 5 min different from mine - I would simply go in 5 min earlier than what my clock said.