Short Volume is a daily figure showing how many shares were shorted on that day in a particular market. (ie., NASDAQ, NYSE, EDGX, ARCA,...)
Short Interest is the total sum if all open/uncovered shorted shares.
FINRA only displays three markets: NASDAQ, NYSE, & OTC. By shorting on only one market, that Market Maker can be essentially held hostage and therefore the PPS can be moved...
Example of “ShortExemptVolume” can be seen in this list: