Function inside an if statement?

I have tried the below and there is an error to getting it to get the last number or something like that. Any help?

local booth = game.Workspace.CreditBooth.Board

local player = game.Players.LocalPlayer

local items1 = {booth.Side1.Credits:WaitForChild("10Credits"),booth.Side2.Credits:WaitForChild("10Credits"),booth.Side3.Credits:WaitForChild("10Credits"),booth.Side4.Credits:WaitForChild("10Credits")}

for _, v in pairs (items1) do
    v.MouseButton1Click:connect(function()
        local num = tonumber(string.sub(v, string.len(v))) -- Error is here.
        local parentnum = tonumber(string.sub(v.Parent, string.len(v.Parent)))
        if num == 1 and parentnum == 1  then

        elseif num == 1 and parentnum == 2 then

        end
    end)
end

Players.Player.PlayerGui.CreditBoothScript:11: bad argument #1 to 'len' (string expected, got userdata)

What you could do is cross-check a >boolean> when executing the >event> code if you're asking how to execute an event only if it's executed another. But, in this case, you can just use two separate events.

For example:

script.Parent.MouseButton1Click:connect(function()
print'1';
end);
script.Parent.Parent.MouseButton1Click:connect(function()
print'1';
end);

local root_folder = script.Parent
-- Direct root_folder to your ScreenGui
local clickable = {TextButton = true, ImageButton = true}
local last_clicked

local function root(object)
	for i,v in pairs(object:GetChildren()) do 
		if clickable[v.ClassName] then 
			v.MouseButton1Click:connect(function()
				print(last_clicked and last_clicked.Name.. " is opened." or  "Opened "..v.Name.. " for the first time")
				-- do something
				last_clicked = v
			end)
		end
		root(v)
	end
end

root(root_folder)