Were you camping without hook ups? If so, my guess would be that the fresh water tank may not had been completely filled. Sometimes there's air in the tank which can give a false "full" reading.
Please wait for experienced members to chime in.
Great choice for "Living within my means" and camping for one...
2011 Salem Cruise Lite 20RBXL & 2011 Toyota Tundra Dbl Cab
Camping History: 45 Trips / 133 Nights / 3736 Miles
FRF Social Group: Campers of the West