So this is how I understood it today at LAX. The signs are ( i think two colors ) one for 1, one for 2. One is for everyone preboarding. Disabilities, with kids, military, GS and 1K. Number 2 is for Boarding group 1. 1 + 2 does no longer represent boarding group 1 and 2. And boarding groups 2-5 are called when everyone else has boarded.