AD8 TA, page-154

Professional short sellers are professional risk managers. This is why most short holdings are an asymmetric hedge against an index of some type not the stock itself. If the market was to make a sudden reverse of trend professional traders want to be able to exit their positions as fast as possible relative to the risk. As days to cover represents the number of days it would take for short sellers to cover their positions based on the average daily trading volume for professional short sellers the lower the days to cover the easier to theoretically manage and enter or exit a market relative to the risk they are prepared to carry. Like them or hate them short sellers offer an insight which may not have been otherwise visible. When you next have time look closely at the top 200 short holdings and their covering days. Hope this makes sense and helps. My opinion only of course!