Firstly, unless you started your Urban Worm Bag with existing vermicompost, do not expect your first harvest until 4-6 months after you started your Urban Worm Bag*and* when the Bag is 3/4 full or more.

Moisture is difficult to manage in the beginning, so expect conditions in the bottom of your Urban Worm Bag to be wet. This will likely result in a lot of worms. Your first harvest may also feature a lot of unprocessed bedding material. 

So you should plan to put your first harvest, and possibly even the second, back into the top of your Urban Worm Bag.

Over time, you will find that your harvests will contain fewer and fewer worms and the moisture will be more appropriate.