6:45a to 7:45 = 1 hour
7:45 to 8:45 = 2 hours
8:45 to 9:45 = 3 hours
9:45 to 10:45 = 4 hours
10:45 to 11:45 = 5 hours
11:45 to 12:45 = 6 hours
12:45 to 1:45 = 7 hours
1:45 to 2:45 = 8 hours
2:45 to 3:00 = 8 hours and 15 minutes
then just add the 28 minutes to the 15 minutes
28 + 15 = 43
6:45a to 3:28p = 8 hours and 43 minutes.
Hope this helps.