Can anyone help with explaining this code?

Question

https://code.sololearn.com/caB0aPZpuhkq/?ref=app

Answer 1

Inside 'when',
Change value of i to 6 instead of 5.
That way 15 will be skipped.

Answer 2

kev_coding I know I'll have to change i to 6 if I want 15 to be skipped but I'm asking why??

The code skips when i is 5 but looking at the comment in the code, when i is 5, sum is 15 and not 10 so why is 10 skipped?