experience
I was told the work effort would be 4 hours in length.
When I made the appointment for the work to be done, the arrival window was 4 hours long, and not stated. This lead me to think work would start at 1000 and end at 1400. I had adjusted my day to have 1000-1400 be your work time on site. Prep efforts were complete by 1000. Later day events had to slide as the start of work did not begin until 1130.