With this you can set the how confident the app (Model) needs to be about the object he detects to register as a count. Only products the passes the threshold will get notified on the screen. With 0 percentage everything the app find as an object he shows and counts if it moved from one side of the line to the other side. 100 percentage you will see only object where the app thinks he is confident that it is the product where he is trained for.

Depending on the model and how well trained the model is you will see difference in confidence.