This graph charts the total AVERAGE Student/Hours per day for each specific classroom. The average is based on the total Student/Hours divided by the total days of activity for the selected period. Example; If the graph reported on this week had a holiday on Monday which resulted in the school being closed, then the total activity days for the period would be 4 rather than 5.
One "Student/Hour" is equivalent to one student attending class for one hour. Therefore 4 students attending a class for 4 hours would result in 16 Student/Hours being recorded for that day.
This can be useful in determining where your "busiest" classrooms are on average throughout the day since it shows the average TOTAL student hours rather than simply the average maximum Attendance.