Similar to ours. We were "estimated" at 15.5k gallons, but filled right at 14k. I think the tanning ledge (similar in total size to yours, it would seem) isn't accounted for in the programs they use to build the design.
We were also stagnant for about 36 hours before starting everything up and giving the first dosing. So far, its been good, so I wouldn't stress too much over it.