Some times an owner will drop off the dog early Saturday morning and pick him up late Sunday night.
First, you find out when the dog is being dropped off and will be picked up. Then you modify the booking to include the overage in hours past the 24 that is included in the "nightly" boarding rate. Since you provide daycare, you would add, at a minimum a daycare charge. However, if the dog is with me more than 10 hours over, then I would add another full nightly charge. It is very easy to do and customers do understand if you explain it to them at the M&G, which is when I ask about their travel plans. I do give customers a few hours leeway, but the scenario you describe would get them another full night charge.