Attempt to perform arithmetic (add) on number and Instance

[TyK214]

You can write your topic however you want, but you need to answer these questions:

1. What do you want to achieve? Keep it simple and clear!
   Fix error

2. What is the issue? Include screenshots / videos if possible!
   attempt to perform arithmetic (add) on number and Instance

3. What solutions have you tried so far? Did you look for solutions on the Developer Hub?
   Devfourms

Local Script:

local amount = child.Num.Value
		
game.ReplicatedStorage.Remotes.ChangeFloorValue:FireServer(amount)

Script:

game.ReplicatedStorage.Remotes.ChangeFloorValue.OnServerEvent:Connect(function(amount)
	floors.Value = floors.Value + amount
end)

[Negativize]

The first argument of OnServerEvent is always (implicitly) the Player who invoked the event. You need to account for this:

game.ReplicatedStorage.Remotes.ChangeFloorValue.OnServerEvent:Connect(function(player, amount)
    print("Player invoked remote event", player.Name)
    floors.Value = floors.Value + amount
end)

Read more here.