When you have multiple 896's or 828's, their order is based on the number assigned to each interface (896-1, 896-2, 896-3). A unit's (896 or 828) "number" as it relates to other units is determined by it's ROM chip. There's no way to change it, even by moving them around to different firewire ports, or changing the order in which they're chained together.
So here's what you could do. With all interfaces plugged in, open a music project with some audio to play back on it. Set the ouput to "896-1 Analog 1-2", and watch to see which 896 plays that back. Then put a little piece of tape with "#1" on that 896. Then set the output of that audio to "896-2 Analog 1-2" and repeat the process, labeling the unit that played back "#2", and so on. That way you can correlate what "896-1" on screen with "#1" in your rack of 896's (or 828's).