Practice makes master.
This app focuses on repetitions. Like a soccer player need thousands of touches on the ball to be a good soccer player, a child needs to repeat a multiplication many many times before it doesnt has to be counted on the fingers.
The parents should encourage the children to do a number of math-tasks. Say 50 multiplications, or 20 subtractions. And then give alot of credit afterwords.
There is also a "Gamemode" where you put a time-limit and see how many tasks you can do before the time runs out.
But in the beginning we recommend to dont have time limit.