question re how code availability works

[princess lovers mom]

wondering if anyone knows how they determine how many rooms are available for code rate?

I know for myself that I reserve the room level that I am willing to pay rack rate for and then sit back and wait for codes...but if i have a ressie and then codes come out is my reservation essentially cancelled and a room that is a code room given to me at code rate and my origainal reservation go back to non code rate...

am I clear...???

do they make a certiain % of total rooms in the resort code rate or a % of unsold rooms?