Its how many units a starting pitcher would have made you if you bet on him all season.
http://www.statfox.com/mlb/mlbteam~t...eason~2007.htm
Just something to play with. For instance, take a pitcher who is up more than 1 unit versus a pitcher who is down more than 1 unit (or any parameter). This has several advantages, such as including bullpen support and leveraging the big name pitchers against their money value.
The statfox link gives an example. Later in the season it would be better to have stats for L5 or L10 starts, instead of accumulating all data from the season.