No rule can make the system more complicated than no system at all.
Start with one shelf. One label. One address. The rest follows.
What building or area are you organizing? Choose a 2-letter code. Common ones on the reference card. Or make your own.
Cut out the N, S, E, W signs from Page 1. Tape to the corresponding walls. Every address references these walls.
Divide your space into areas. Each gets a 2-letter zone code. Post the zone sign from Page 2.
Standing at the anchor wall, number shelf columns left to right: N1, N2, N3. Every position now has a unique address.
Add shelf level: T (top), M (middle), B (bottom), F (floor). Name items noun-first on the Avery labels. Stick them on.