I never really paid much attention to this in the past but it's bugging me tonight. I have just inserted an instrument track with Kontakt 5. The track is immediately named as "Kontakt 5 6" but in the rack, the synth is named as "Kontakt 5 4" -- why? The automation field in the synth rack says "Automation: Kontakt 5 6."

Is this just another oddity, or am I misunderstanding the naming convention here? 

I always thought that the final digit referred to the number of instances that were running in the synth rack.

I've yet to see a situation where there was a discrepancy.

if you solo it via Track View, does the "wrong" one also get solo'ed in the rack?

Oh yes, there is no doubt that the track is pointing to that synth. I had the synth rack open when I create this track and saw immediately that the synth that appeared in the rack had a different name from the track. This is why I probably got so confused the last time I attempted to clear the rack of unused synths.