How to change Met Level

[Anvysauce]

I was messing around with the bytes of a Pokemon, for context it’s in Platinum and came from Red, but for some reason the met level is showing as “Met at Level 100” and I was wondering if this could be changed, or if this is a natural phenomenon, because it reached Level 100 in Emerald

[BlackShark]

On the transfer from Gen 3 to 4 the met level is set to the Pokemons current level.