GeeJay2000,You are on the right track. Here is a review of the basics (as I understand them.)
When you create a list of passwords two list of numbers are generated. The first list is the Key Code, which is number from 1 to "whatever number of passwords you selected to generate." For each Key Code there is a corresponding Registration Number.
The Key Code that is selected is based on the serial number of the hard drive. This is important because when someone gives a friend a copy of your ebook there is less than .1% chance of the two friends having the same Key Code.
Let's say the ebook gives the keycode 326. What it is asking for is the Registration Number that corresponds to number 326.
Your life will be a lot easier if you consider using an Automatic Payment System like MicroCreations. You can find them at:
http://home.att.net/~microcreations/
Currently, I'm waiting for them to complete the APS for 2CheckOut, which I prefer over ClickBank. The last I heard is that it should be soon.
Hope this helps.