Hi. does anyone know the age difference between garys character arnold and his age in real life when the show ended? i know arnold was 8 when it started and gary was 10 and was on show till he was 18. but from my understanding arnold only got up to 13.
this may sound confusing but can anyone help?

Often shows do that. They slow down how old they are getting. Willis was in high school in the 3rd season and he went to college in the 8th season. He should have gone in the 7th season.