I am trying to make it so that also when you join the size of the part goes up.
local leaf = script.Parent -- 'leaf' is a part game.Players.PlayerAdded:connect(function() leaf.Size = math.random(5-10), 1, math.random(5-7) -- error on this line end)
You forgot Vector3
local leaf = script.Parent game.Players.PlayerAdded:connect(function() leaf.Size = Vector3.new(math.random(5-10), 1, math.random(5-7) )-- error on this line end)