What is the parameter at the end of the event ClickDetector for how many times they clicked?

ClickDetector#MouseClick returns the player instance of who clicked it, not the number of times the ClickDetector has been clicked. You can record this though! Let's create an instance that can log it.

Create an IntValue and set it's parent to the ClickDetector, and name it to "Clicks". Now we will reference it in the script and add on the clicks.

game.Workspace.Part.ClickDetector.MouseClick:Connect(function(player)
    ClickDetector.Clicks.Value = ClickDetector.Clicks.Value + 1
end) 

If you want to get the amount of times it has been clicked, then you can get the value of the IntValue.