See discussion here: http://moodle.org/mod/forum/discuss.php?d=195093&parent=850046

When editing an appointment slot, all of the slot's settings become reset instead of retaining their previous state.

To test:

1. Create a scheduler
2. Create an appointment slot with settings other than the default and save
3. Attempt to edit that single appointment slot

Instead of the slot's settings page having retained the saved values, they are all reset to default.

This is more of an annoyance than anything. If you are trying to change just one of the variables within the slot's settings, you must take care to remember the other settings or else you risk creating appointments with the wrong information!