These functions don't add or subtract 1 when a child is added to "new."
local num = script.Parent.Parent.num
local new = script.Parent
new.ChildAdded:connect(function()
num.Value = num.Value + 1
end)
new.ChildRemoved:connect(function()
num.Value = num.Value - 1
end)

4 comments
new.ChildAdded:connect(function(CHILD) end) <-- You're missing that one argument.
Why do you need to do something like this?
@AstrealDev That's not the problem w/ his script...
Did you check the Output for errors? Via for studio, or F9 ingame? If so, could you please provide what it said?