Maybe the reason that numbers are lower is because they are gradually moving people off the waiting list and into the 'in progress' stage (i.e. if they release ten more orders to In Progress, your priority waitlist number will drop by ten.)
I think nasa25 is actually right. Here's basically what I posted above just a few minutes ago (but seems to have been deleted?):
I currently have 2 reservations for a 6+ 64GB Space Grey.
One is a "new line" reservation - which dropped significantly from #106 to #52 (which corresponds exactly with jnhs's new line reservation drop for the same model/specs) - since last night to just a few minutes ago.
My second is an "upgrade" reservation for the exact same phone but it only dropped from #469 to #462 during the same time period.
Priority definitely seems to go with new line reservations.
Will they send us shipping information for our IN PROGESS iPhone 6?