I can't answer your question but what is a +1 leap?
Arriving on one train heading (say) north and immediately returning 1 minute later on the train going in the opposite direction (in this case south).
Sometimes it is possible to have a "minus leap" where the publicly advertised departure times of the trains don't take into account the unadvertised earlier arrival times. So a train advertised (with a single arrive/depart time) of 1404 may actually safely connect into one departing (in the opposite direction) at 1402, giving you a "minus two leap" or "-2 leap".
Often where trains cross on a single line such as the West Highland Line they are timed such that the first train to arrive is the second train to depart. Remember the trains have to exchange tokens (originally with the signaller at the station, nowadays with the RETB system controller), so a stop involving an exchange of tokens (where trains cross) is bound to take a little longer, and the timetable is planned accordingly. If an actual swap of train crews is involved (and I don't have the diagrams, sorry) then the planned stop will be even longer.
