It very well could be 15 feet. Size of the animal was never in question, but... since he cleared the enclosure questions in a later reply, and stated that the enclosure was temporary, i dont have any actual beef. That is just something that i question.. because i feel, personally, that it was just too small as a permanent home.
I used the Snake Measuring program... and... if you look at the bowl in that enclosure, they are 11" from one end of the base*underside of the bowl* ( longways) to the other, i rounded it off, and made it 12 to leave room for any error, and to make calculating it that much more simple. i came up with 15'.
If that bowl is in fact larger, then, forgive me. But i believe that is the largest size they make... at least, in that shape.

* i have one*