Calling all Subway buffs

[RDU-JFK]

Does anyone ever notice the small numbered square stickers by the doors on the subways? Well I have seen a sticker of the same size qith a black star on it next to, or near these numbered stickers. What does this star mean? I've seen it on the Q, B, D, and N trains. Any insight is appreciated.

[USAF Pilot 07]

I believe it indicates the door panel. Since train cars can get turned around, or at some terminals loop around and at others depart the way they came in, I think those stickers are there to alert crew and mechanics to the proper door panel, so that if anything happens, the door with the problem can be found quickly...
I'm not 100$ sure though...

[RDU-JFK]

I thought it was something like that...thanks!