One Listing Only button

I have a question for the person who designed this car dealer theme.
What is the use for this One Listing Only button?
Let me explain I add a listing package but I want my customer to be able to place just one listing if the customer wants to place 2 or more listings he have to pay, however if I enable the One Listing Only button than they can’t upgrade to the membership because this One Listing Only button is enable what the question is if I can’t use the membership feature what is the purpose of this button?

If I disable it the customer can place as many listing as he wish without paying and if I enable it they can place one and they can’t get access to the membership because it won’t allow them to place more listings .. Such a pain in the B…