Thanks for that feedback Pascal. That may be a bug as it should chnage at 5 minute intervals.
Often the - and + buttons do not give a chance to set an exact start time.
E.g., if I wish to set 8:40 and the timer is currently at 8:50 a click on the minus button will change it to 8:44 and a second click to 8:39. The slider does not help with better results. Why is that? Wouldn't it be great, if one could simply enter the exact time of start?