The system will have automatically put in the numbers based on the reps and weight you prescribed in the work out. These numbers will be faded slightly and made darker if the client presses the check mark or complete.
Additionally, they can overwrite the numbers if anything is different.
Small thing but can save time by just pressing the check mark.
This can also be useful for exercises that are just done for completion, and just reps (mobility exercise, foam roll, warm up etc etc)