Rep Timer helps you build muscle memory for slower reps. Slower reps helps in developing greater muscle mass over time. It also makes exercises alot harder so dont panic if you need to lower the weight a bit :)
Simply do the rep in the same speed as the ball shown in app. Its two seconds concentric movement, one second rest, two seconds eccentric movement and one more second rest. This repeats for all reps.
You can choose how many reps you want to do, when that amount of reps is done the rest timer starts. This is to show you how long you have rested. At any time in the rest section you can press the play button in the bottom left corner to get back into a new set. If you are done, or just want to start over, you can simply press the back button on all screen in the bottom right corner.
Try it now! :D