It’s like when you use TMap (not sure if you’ve gotten to that part yet), all it’s doing is using types that you’ll usually use in your Unreal code in the future. Both int32 and int are valid types, so that’s why it compiles, though the size of int is implementation-based. Because of this, int32 is usually used in UE4 code to keep things working cross-platform.
EDIT: Can’t figure out strikethrough on here, but what I said was wrong. At this point int is pretty much always the same as int32, but the innards of UE4 use int32, so I’m guessing that’s the reason you’ll want to be acclimated using it.