At the summit: the schedules of return are free.
The guide, can reserve his places for the return trip. For that, he has to, by arriving at the summit, appear at the station manager and reserve the schedule of desired return.
The guide will then have to appear with his whole group, 10 min before the schedule of return which was indicated to him.
If he does not want to reserve his return, the group and his guide will appear at the station of departure with the individual.