Attempt to perform arithmetic on a nil value?

if Counter.Text ~= "0" then
								Counter.Text = tostring(tonumber(script.Parent.Loot.Inventory.InventoryScroll:FindFirstChild(v.Name).Counter.Text) + 1)
							else

It gives me this error:

Players.Player1.PlayerGui.CoreGUI.Core:102: attempt to perform arithmetic on a nil value

Counter.Text is not a number
How many did you say?

If you use tonumber on a string that has no implicit conversion to a numerical value, it will return nil. You will need to add a condition to catch that.