MarketForce…confused on what to do?

Can someone please explain how it works? I’m looking at a Dine-In shop but don’t want to accept the assignment without completely knowing what to do.

It says the shop fee is $20 and then next to it there’s a box that says make an offer. What does this mean? Do I need to pay-in?

Below that, it states that the meal reimbursement is $14.95. So That means I pay for my meal and they’ll pay me back later, right? So what is the $20?