You could handle the Prompt deactivation on the client side perhaps?
local Player = game.Players.LocalPlayer
local leaderstats = Player:WaitForChild("leaderstats")
local Stat = leaderstats.Number
local Prompt = workspace.NPC.Head:WaitForChild("ProximityPrompt")
Prompt.Triggered:Connect(function()
Prompt.Enabled = false
Stat.Value += 1
end)
If you want the values to change from the server side, you’d need to use RemoteEvents to handle client-server transportation