An example Saturday
A solo detailer books a full detail at 8:00 and promises a second full detail "around noon." Service time says that works: 8:00 to noon, noon to 4:00. With 30 minutes of setup and pack-down per car, a 25-minute drive and a 15-minute buffer, the first car is packed and buffered at 12:45, the second arrival is 1:10, the detail itself starts at 1:25 and pack-down ends at 5:40, forty minutes past a 5:00 finish.
Telling the second client 1:10 instead of "around noon" costs nothing at booking time. Arriving 70 minutes late costs a review.