As with many of Lynch's projects, numbers play a role in the puzzle. Here are some of the numbers thus far revealed in The Return. Feel free to add ones that you have noticed!:
"Remember 430" the Giant says to Coop in the new Black and White room with the Phonograph. This number has yet to explicitly come into play.
The Arm says to Coop "253 time and time again" (this is revealed to be the time Cooper transports back to reality) as shown on the American Girl's watch (Notably played by Phoebe Augustine : Ronette Pulaski !)
The speaker grille/outlet apparatus through which Cooper is transported to the "real world" first reads 15, and after Naido (the eyeless woman) resets the breaker it reads 3. I believe this has some correlation to Coops #315 room key for the Great Northern.
Richard and Linda ...Two birds with One Stone.
"119...11.9......119.....119!" The drug addict mother says before taking her last pill with whiskey.
Not necessarily. Lynch has a penchant for non-linearity, and often times uses circuitous or mobius-like structures in his editing (the waiting room of the Black Lodge is a prime example). The order of the numbers may not be "logical" to the extent of being exactly replicated (315 to 315), but the fact that the same three digits 3-1-5 are present in both situations (the real world and the purple room), and that they would be scrambled in the purple room (which has a bizarre stuttering time signature) makes sense within that context. 315 is "home" for Coop, so I imagine the use of those specific digits suggests that going through the outlet will take him "home" or closer to it. The scrambling of the numbers could also foreshadow that Coop is NOT going "Home" perse, suggesting with numbers that some kind of switch has occurred (as we discover it has, with Dougie). As I write this, Im thinking that just because we are shown 15 first doesn't mean that the number should be perceived 15-3. Lets say that the outlet is a threshold, a centerpoint, and extending out from that center in time is first the 3 (as it reads during Coop's transposition) and then the 15 (as it reeds when coop first enters the room). In that sense, we can perceive the number still as 315. Lynch really gets the mind reeling!! In a good way. That said, we may find other uses of those numbers later in the series. Looking forward to it!
Regarding 15 and 3. It just struck me that 15 and 3 could mean the same thing, just written differently. That is, as in "3 pm" and "15:00 hours". It's an alternate version of the same outlet? I have no explanation though as to why there would be times/hours on the outlets since it doesn't represent the time he goes through (which is 2:53).
I think the drugged out mother calls out 119 as part of magical summoning of the demon Halphas with the aim of protecting Dougie Jones. This entity's name in Hebrew ads up to 119 according to Aleister Crowley's Sepher Sephiroth. The letters that spell the demon's name in English are H E L P. Call for help.
Crowley, by the way, is mentioned in Frosts's The Secret History of Twin Peaks.