In my understanding this calculates times by checking if the MOD of 'Actual Minutes' / 5 is equal less 2 or equal more than 3. Afterwards adjusting the start time in parts of 5min. Works all well, as far as I can see.
But when it comes to select a start time, the query always sends a 'No rooms available' back, when the start time is unequal to a full hour or half hour (like 09:25). When the start time is equal to a full or half hour (like 09:00 or 09:30), available rooms are shown properly.
I really cannot find any other variables or settings, where I can adjust that 30min grid to a 5min grid.