Color Mask Tool - Smoothing and Tolerance sliders.

Hi Guys,  I've searched Corel's help files, the knowledge base and You Tube without any answers.  I wanted to ask if someone can add some detail for the two sliders in the Color Mask tool.  I can see some visual changes when adjusting them but am not completely sure what they are each adjusting.  Just wondering if someone can add some feedback.  Cheers.