Having trouble adding two number values together?

Im making a simple tycoon and for the droplets that fall from the dropper, they have a numberValue of 1. The collector also has a numberValue, when the droplets fall on the collector the collecotr's script is supposed to add the value of the droplet to itself but i keep getting an error

Code

script.Parent.Touched:Connect(function(hit)
    local coin = game.Workspace:WaitForChild("coin")
    if hit == coin then 
        script.Parent.Value += 1
    end
end)

error

Workspace.Collector.Script:4: attempt to perform arithmetic (add) on Instance and number