Press the S,D,F,J,K,L keys and wait until the green dot shows. Once it does you may let go and solve your cube. After you have solved your cube, press space bar and your time will appear. Make sure you press "Reset" button or press the "C" on your keyboard to clear the time before you attempt another solve.
This timer doesn't calculate averages like the previous one and this timer only goes up to 9:59.999. Previous timer: https://scratch.mit.edu/projects/68727840/