Making sense of some ZDB output...?

[Zaphod Beeblebrox]

In my quest to recover files, I've come across something I don't understand.

          100000   L0 1:720cfa33400:24c00 20000L/20000P F=1
B=11756828567/11756828567
          120000   L0 0:94048dc9000:24000 20000L/20000P F=1
B=11756828567/11756828567

So far, files I've recovered have been on vdev '0' ... which has 9
devices... I therefore makes sense to me that 24000 (hex) bytes is composed
of 20000 bytes of data and 4000 bytes of parity.  But this object I'm
trying to fetch has some data on vdev '1' ... which has 8 devices.  24c000
/ 8 is 4980 ... which isn't a very even number.  Am I looking at this
wrongly?  Does the size include the parity or not?