Why does my code for pvz Garden warfare work twice

[Fair12a9]

So a couple years ago my brother bought Plants vs zombies garden warfare download code for pc and he did use it but now after 8 years i can suddenly use it even tho he used it a long time ago and iam just checking and not just using it because i am scared that he will lose his progres and the game but does that happen or is it fine to use it again?