From my experience the numbers left of the colon are minutes and the numbers to the right are seconds. The seconds count down to 0 and then reset to 60 as the minute count decreases by 1 For whatever reason I actually get a tiny kick out of this weird behavior and almost always set my microwave for X minutes and 99 seconds (also almost never 100%power), my favorite part is adding 30 seconds with X:60< <70 so in theory it should be able to just go back to 9x but it always jumps up a minute and adds 30 instead. It knows 99 seconds is silly but still let's me do it.