I've just been having a look at the Stargate Universe Season 2 checklist, and noticed this running across the top of the page:

Extremely Limited = 200 or less, Very Limited = 200-300, Limited = 300-500 range, Normal = over 500

I'm assuming that it would be a category that contains the 1-, 3-, and 6-case auto cards, but I guess we'll find out soon.

I don't think RA means to include case autos in the extremely limited category.

Incentive cards are judged by the degree of product necessary to obtain them, so they are all on tiered, limited production levels. They are not packed pulled, so there are no stated ratios, and their actual numbers are usually only calculated by collectors based on the reported number of cases released.

Extremely limited is just a catagory for those premium inserts that fall in the shortest run of production, be it a certain signer, or a specific prop card, or whatever else may be the type of "hit" in the product.