Some insights on Napoleon Hill

A while back, a bunch of guys on this forum were having a discussion on
Hill. After he wrote think and grow rich, he continued studying the field.
In the 50 or so years he studied the field, he identified 17 principles of success. The final piece of the puzzle he called cosmic habitforce.
If you do all the preceding steps, your habits will lead you to success.

The only problem I have is if there are 13 principles in think and grow rich and 17 principles in the science of success, it would seem that he found 4 more principles, right? But the 2 lists don't match up. Did he discard parts of think and grow rich? Hmmm...