Most crafting rolls are based on ability scores. In the case of Alchemy, this is your Constitution and your Intelligence. I don't know what the others are based off of, off-hand. If you see a -5, that means it's a recipe you don't know yet. Once you do know the recipe (have succeeded at making whatever it is your crafting), the -5 goes away. The last number is crafting level for that particular trade.
So, if I was a wizard who had 12 CON and 18 INT trying out a new recipe for the first time, I would have something like X + (4+1-5+Y), where X equals my roll and Y equals my crafting level in alchemy.