It's a difference in amount/heat of kilining. The higher the number before that L the more caramelized it's become. They'll be darker in color and flavor, but more like cooked sugar than roasted coffee.
On Deck: Chav Irish Red
Pipe Dreams: Chai Porter
Primary #1: Empty
Primary #2: Empty
Primary #3: Imperial Oatmeal Stout
Bottle Conditioning/Drinking: Brown Porter, Pale blonde session ale