short sale price as % of appraisal

[Laura Turner]

Sorry for the re-post, I couldn't change the title of a similar post so am being more specific with this title in the hopes of receiving more information.

I've heard that on a short sale, a bank will accept a certain percentage of their appraised value. Is there any rule-of-thumb for what % of the appraised price a bank will accept? And what is that based on? What factors can affect what the bank is willing to accept?

The seller's delinquent mortgage is apparently not an FHA mortgage.