This is the script:
function onTouch(hit) mouse.Button1Down:Connect(function() if hit.Name == "Sand" then hit.Size = hit.Size -0.1 end end) end script.Parent.Touched:Connect(onTouch)
You cannot decrease a part's size property that way. You need to reduce its size by using a new Vector3. Also I'm not sure why you are defining Button1Down inside a Touched event, but I'm leaving it there anyways.
function onTouch(hit) mouse.Button1Down:Connect(function() if hit.Name == "Sand" then hit.Size = Vector3.new(hit.Size.X - 0.1, hit.Size.Y - 0.1, hit.Size.Z - 0.1) end end) end) script.Parent.Touched:Connect(onTouch)
Ok here is what you are doing wrong. First of all, I think you should make this script a bit.... easier to read. Unless you are going to use that function again you should probably format it differently.
script.Parent.Touched:Connect(function(hit) end)
Instead of:
function OnTouch() end script.Parent.Touched:Connect(OnTouch)
Ok so now that that is over with, you need to change line 4 to this line:
hit.size = hit.size - Vector3.new(0.1, 0.1, 0.1)
If there is still a problem after you do this, it is most likely NOT the size.