Nuitrack error

vvvv gamma question
1

Hi, I´m using nuitrack in VVVV to track the silhouette of a person and it works fine.
However, when the first person leaves the scene, another one enters, and the first one returns to the scene, he appears as a “ghost”, with only its contours.
I want to track only one person, so the software needs to forget the first user and jump to the new one. And if there are 2 people in the scene it must view only one.
I had already changed in the config file “ActiveUsers”: 2 to 1, but it didn´t work.
So how do I track only one person and not getting this “ghost” image?