We had a microwave in the office that auto started based on whatever number you pressed. If you wanted to type in 45 seconds, you would press 4 and it would instantly start running with 4 minutes on the timer. Everyone just pressed the "+30 seconds button" until it was close to the time they wanted and then stopped it manually to get it more precise.
If I remember right the solution was to press "Cook Power" then type in the number of seconds. There was nothing on the microwave to explain this, I had to look it up online.