> However,
> for K-O, it says BOTH K-O preferred AN I18
> and Fab4. What does that mean??

Off the top of my head, I think I remember that KO Preferred is a technique whereby you do not use an individual and unique RC for each index you use, but rather you group the indices into one of 3 (I think) categories, and use the same single index value for each member of the group.

So, I used the Perferred indices, and assigned one of the group's RC to each of the I18 and F4.

"Preferred" and "I18 F4" can exist together.