Pagliacci's Delivery Service Fee

I know this is probably adding to the debate about tipping, but after a couple of deliveries I finally just now noticed that Pagliacci adds on a delivery service fee to help pay for their employees wages.

I've actually never eaten in a Pagliacci, so I don't know if they add this fee everywhere or just for delivery? I'm assuming just delivery since it says it's a delivery fee.

So is that the tip? Do people add on an additional 15% or 20% tip on top of this fee? I don't mind tipping, but this seems like a lot. I know that when I eat in a restaurant that has a mandatory service fee, there's no expectation to tip on top of that.