In PLN [Not implemented]
AttractionLink <TV> X Y
the TV on the AttractionLink represents the difference between P(Y|X) and P(Y|Not X). For instance if X and Y are concepts, the strength of TV (letting aside the influence of confidence for now) will be
TV.s = max(0, TV1.s - TV2.s)
where TV1.s and TV2.s are defined with
InheritanceLink <TV1> X Y
InheritanceLink <TV2> Not X Y
It is therefore not a probability (or at least not obviously so).