yeah it confused me too, but what i chalked it up to being is they can only have XX number of computers in production at a time (limited staff and space) so once your order hits phase 3 it just sits there till your # is up.
Phase 4 must take very little time, being i have yet to hear anyone even seeing it, just 3 --> 5
also being their phase system isn't automated, at least as i understand it, at best it will get updated once a day, for the progress of that day.
still fairly small company, and the process of production is pretty involved, like Hammerhead has mentioned, they don't just have the systems sitting on a shelf to slap a couple hard drives in and off it goes

what would be kind of neat is like a #d queue to look at like, you have 204 computers ahead of you in queue... but then they might get more people mad in seeing there are cases where orders are pushed ahead of others in queue...
also trying to give a estimated time for the length of a queue would be very difficult, being if there is a problem with a computer it goes back a couple steps in production, not re entering the queue line, it delays the orders behind it as well
but then don't quote me on any of this, just pure speculation ;D