Casio CZ/ VZ/ FZ - Pro Series

Hello! First of all, 16-note polyphonic means that I can play 16 keys 
at the same time (if I had 16 fingers obviously... lol) and all they 
would suond!?
I have a CZ-1 and if my concept about 16-note polyphonic is correct my 
Synth isn`t working fine... In the manual says that 16-note polyphonic 
is possible if I choose line 1 or line 2, 8-note polyphonic choosing 2 
lines, 4-note polyphonic in tone mix mode and monophonic in solo mode.
My problem is: I play any preset tone and choose line 1 only or line 2 
only and I can play 8 notes at the same time...
Is it normal?! Am I wrong with my concept about 16-note polyphonic!? Is 
my Synth maybe damage?!
Is it possible to play 16 notes at the same time with a CZ-1!?
Sorry about my ignorance with this stuff, I love my CZ-1, but I am very 
new in synths

Thanks for your time!!!

pHede
Bs.As. Argentina