Press space. You will have 15 seconds of inspection but you must press space again to start your time. The to end the solve is by pressing space again, At the end of each solve you will have 4 seconds to press either press "O" for DNF or press "P" for +2. Your time won't show up until you wait 4 seconds. Your time will show up after that. You can use any cube you like although the more time you take the higher chance of the timer failing to calculate.
DNF: Means that you did not finish the cube and it will say DNF on your time. If you get 2 DNF's your average will be DNF. +2: Means that you are one move from being in a solved state and it will give you +2 seconds to your time. THIS TIMER CAN FAIL TO CALCULATE YOUR AVERAGE ANYTIME. This timer can go up to an hour and a half and nine minutes. The way the timer calculate your average is by taking the best and the worst time that you had away and adding the remaining three together and dividing it by three.