"Days to cover" means how many days given the average daily volume it would take to cover all of the short positions. The greater this number the greater the potential short squeeze rise. Most of the shorts would try to get out quickly so this would cause a volume spike and volume pushes price in the direction of the trades. Imagine 13 million shorts trying to buy on a permit announcement at the time when longs would have no reason to sell just yet and institutions are taking more interest.

The other factor to look at is % of float, which is the % the short shares make up of the total available shares. In KRY's case this is low so while the days to cover indicates a potential nice surge, it will be short lived.