If you sound it out loud, you'll notice a pause (very slight) after saying "cua"
If you break it down:
"Cua-les" = 2 syllables
Another example:
"Mike"
Mi-ke = 1 syllable
sounds awkward when you try to break it down; doesn't fit.
Just see where you can break it down and it has to sound right on the tongue when you do.
Hope that was helpful.
Cheers,
