What do the symbols mean on the level packs

[Hypernova]

I just finished new adventures (i think) and i have 2 yellow circle things on the level pack, a star and a flag. It looks like there could be room for a 3rd one but I'm not sure. What does this mean? thanks

[Randomiser]

The star stamp is gained by 100% completing a pack. The flag stamp means you won the pack by completing a level with the 'END' property. New Adventures doesn't have a third stamp, but you can see on the main game's save file that you get it from the true ending. So you have indeed fully completed New Adventures!

Not all level packs have a star stamp set, so if you're playing a custom pack but don't see one after winning everything, it could just mean the author didn't set one.