Quick Caddx NX8E zone doubling question

If I enable the zone doubling on the CADDX NX8E alarm panel can some
of the zones also be single zones? If so, what value of EOL should I
use for the zones not being used as doubled zones? If all zones must
be doubled then how do I handle an odd number of zones? This has got
to be an easily answered question, I just don't see it anywhere on
this site or the manual so far.

Thanks,

- Russ