The Cromford Report defines days of inventory as 365 X active listing count divided by sales per year. So for Aviano that would be 365 X 21 divided by 54 or 141.94 days of inventory.
There was one sale in August. Check out the solds sheets under the "Aviano" tab - Aviano Solds page.
Contract ratio is defined as 100 X (pending + UCB listings) divided by active listings. That would be 100 X 5 divided by 21 or 23.8. This measures how hot a market segment is. Typical value for a normal market is 30-36.