Great question.
When you go to the gym, dojo, academy, you may find yourself typically on a 'mat'.
It's what we call time on a mat or 'mats' aka mat time.
If you went to your practise twice a day, three times this week, you'd have 2 x 3 = 6 mats this week.
Just make sure you only register your number ONCE per week as the calculator only calculates it assuming each entry is for ONE week.
You can find your mats entry on your dashboard/edit record/mats.