If there's more in there and it ain't coming out, it's because it's gunked up on the walls of your colon. It took me four years of dedicated cleansing to clean up my poor abused colon. If you are concerned about this, I would steer clear of the P&B while fasting, and seek out a really good professional colonic person to help you flush out the trash. I could never have done the work without fasting and pro colonics.
Save the P&B for a good cleansing diet post-fast. This will also help keep off the weight you lose during the fast, a nice plus!