Jackson owes his sister Monica $15. Explain the meaning of zero in this situation.

accounting wise, if a value is positive, is an asset, you're above water, + 50, you have 50 bucks in your account/pocket.

if a value is negative, is a liability, you're below water, - 50, you owe 50 bucks, you're in the hole for 50 clams.

so Jackson owes Monica $15, he's in the hole for 15 bucks, namely his balance with his sister is - 15.

if he pays her $1, he owes her 14, so - 14 is his balance, let's make a quick table of that

pays her 1 ... - 14

pays her 2 ... - 13

pays her 3 ... - 12

and so on

pays her 13 ... - 2

pays her 15 ... 0

0 means, he paid her in full.