I have used SRAM groups except Red.
So for the other groups... In the smallest cog, the right lever usually is limp indicating it is at the highest end (like a empty trigger, if you will). Just alot of play to let you know there is no more, Double click will go into second cog.
I just installed a SRAM red right shifter, keeping the rear Apex RD, and now it is different. In the smallest cog if I push the lever it would immediately make the RD move towards the second cog, the first audible click will latch on the the second cog. If I do a double click it goes to the 3rd cog.. so, it seems kind of confusing.
All I can think is that this is the zero loss feature, that there is no more limp trigger? Or that, the first click while in the smallest cog is inaudible. Did I mess something up?
Hmmm. My bike's put up for the winter so I can't check off hand, but I don't believe I have that feature with my Red front shifter. I believe it needs a normal double click to get from the smallest cog to the next one larger. At least I've never noticed any different shifting there compared to all the other downshifts in the rear. I wonder if your outer stop needs to be backed off just a tiny, tiny bit? It's been a while since I installed my RD, and I can't remember if the jockey wheels are supposed to be right centered with the smallest cog, or a little bit outer or inner, but you might double check the Sram instructions on that.
And I think I would have noticed because I definitely noticed a fairly common issue on the other end of the cassette - before I tweaked my inner stop just a little bit, I'd often accidently shift off the largest cog to the next one down, and I was annoyed with this (even though I could avoid it by simply remembering I was in the lowest gear back there). After the little bit of careful tweaking, it now gives me a ghost click and stays put.