Question about the 8-A rating in Grappler Baki

[AceOfSpaces3709]

I wanted to ask where does 8-A Attack Potency/Durability rating comes from in Grappler Baki, I originally thought it came from Baki and Yujiro's Skyscraper Feat but I quickly learned it wasn't an accepted calculation. I also thought it had something to do with Baki's Demon Back/Imaginary Yujiro feat (Considering Baki's Demon Back doubles his power and the Imaginary slam was estimated to yield 84.8 tons. Obviously multiplying the latter by two would in turn equal an 8-A rating) but that doesn't appear to be the case either. So where does the 8-A rating come from?

 

[AceOfSpaces3709]

Bump

 

[ShadowWhoWalks]

It is based on upscaling from a 8-B+ earthquake calc without using a multiplier: Calc 2: Baki body slams himself
(Calc 1 in the same blog is the rejected skyscraper shaking feat)

This is the thread where the upscaling was applied:

https://vsbattles.com/threads/baki-strength-crt-round-2.119436/