client wants me to walk dog/bring him to the dog park for 2 hours and booked for only 1 30min walk, what do I do?

I was contacted by Rover last minute to walk a dog for a couple that had to find someone to take over their usual walker's schedule because she was injured. Then they were stood up by a Rover walker for a meet and greet. They contacted me and I accepted. It states clearly that the price is per 30 minute walk. During the meet and greet (which was maybe 11 hours before the first walk) they informed me that the dog needs 2 hours of walking/dog park play. I explained to them that the fee is for 30 minutes and this was last minute, I had other dogs to walk that have been booked for weeks. They explained that they were not worried about the price because Rover was going to cover the difference since it was Rover walkers that had bailed. All went well and I did what I had to. They just found out their regular is still injured and asked if I could do two more weeks. They booked it as ONE 30min walk a day for 4 days. I hit book because I wasn't paying attention and they are repeat clients so I assumed they just knew the drill.

For 4 two hour walks I am only getting paid $70 and that is not subtracting what Rover takes. Is there a way to fix this? Should I bring it up to them? I know I hit book without looking at the details. I know that part was an accident but I am losing a lot of money. Any tips???