I must have explained it wrong. I’ll explain it again. The player has (for example, a number) on the screen, and the other players can change this number. For example, the number 10. Some players made the number 9, and the second player, when he came in should see the number 9. Then for example the first one will leave and the second one will change the number to 8. And when the first one comes in again he should see 8. And so on. That is, this value must be the same for all players.

Use DataStores, its a simple but useful service.

Heres a start: Saving Data | Roblox Creator Documentation