Craft is used during the last step (step 3) of setting up a batch in the Brew Menu.  The Craft attribute of each of your team members is added up into a pool, labeled "Craft Points to Spend".  Unlike the other employee attributes, Craft can be used differently each time you brew depending on your needs for that batch.  You can spend the points to: 

  • increase Yield (number of units produced in the batch)
  • increase the Speed of the brewing
  • or increase the overall Quality of the brewing. 
You can distribute the points in any fashion you choose, they don't all have to be used for the same effect.

Leveling up an Employee's Craft attribute will increase the "Craft Points to Spend" that you see in step 3 of the Brew Menu, so you can have more versatility each time you brew.