When you reject workers on Mechanical Turk, they are not paid but do count toward the overall progress of your study. To replace rejected workers, follow the steps below.
To replace rejected workers from an MTurk Toolkit study, you should Copy your HIT and open a new study for the number of workers you rejected. When you copy a HIT, the original study is automatically excluded from the clone. Thus, copying a HIT to replace rejected workers is quick and easy.