Units of CostOfNonAssignment in assignDetectionsToTracks

I'm having a little trouble understanding what units CostOfNonAssignment is in when employed in the built in function CostOfNonAssignment. My specific situation is I am using a cost matrix based on distance values (lets call their units "distance units") showing how far new detections are from current tracks and I have a CostOfNonAssignment of "n" where n is a positive integer. My assumption was that if a new detection appeared and no pre-existing track was within n distance units of said detection that this would result in a new track being created and if there was a preexisting track within n distance units from the new detection the new detection would be assigned to said track.

Specifically I've been using a value of 20. But strangely enough when I drop the value below 20 suddenly almost nothing is tracked anymore. I have to imagine that this number (CostOfNonAssignment) is not working at all the way I expected it to. If anyone had any insight into how the number works or how I could properly manipulate it I would be eternally grateful.

[Horst Steuer]

Perhaps this answer helps in this case: https://uk.mathworks.com/matlabcentral/answers/308185-assigndetectionstotracks-with-parameter-of-costofnonassignment#comment_568644