I assume it's just your score.

That's King Dedede's number. Call it for a good time.

Older Kirby's were part of the older "score attack" generation of games. Holdovers from their arcade roots.

That's just the score you got during the game. Super Smash Brothers has the same mechanic, literally.

Newer Kirby games dont focus on score anymore.

Classic game, try Amazing Mirror too!