I am using liganProfiler to identify potential targets from the PharmaDB database. The results are provided with a FitValue score. Does this depend on a number of pharmacophore features?  

I am curious to know how this FitValue is calculated. The help document does not provide any detailed descriptions of the parameters used for calculating the FitValue score except for the sentence, "A measure of how well the ligand fits the pharmacophore. The higher the fit score, the better the match."

Also, what should be the appropriate cutoff of the FitValue scope?