In the Defense Trainer, I've had a couple of times where I've discarded a tile that I thought was suji (e.g. 6s when the riichiing opponent had already discarded both the 3s and 9s) but wasn't, as well as a couple of times where I didn't discard a tile that I thought wasn't suji (e.g. 1m when nobody had discarded the 4m), but which I should have because they were. Am I misunderstanding suji, or is this a bug? If it's the former, is there documentation on what counts as suji and what doesn't?
Viewing post in Mahjong Efficiency Trainer comments
I had a similar problem, but eventually figured out what I was missing.
For the former case, I assume either the 3s or the 9s was the riichi tile. Generally speaking, suji information from the riichi tile is considered less valuable; for the purposes of this trainer, the riichi tile should be ignored when determining suji by the standard "three away" method.
For the latter case, there was probably a wall on 2m or 3m. If you can see all four 2m or all four 3m, the attacking player is obviously not holding 23m; so 1m can be considered suji.
I think one-chance is when there's three copies of a tile out or in your hand leaving only one possible for an opponent to have. So if you have a 1 and you see three 2s out, you know the chances are way slimmer they have the 2 and you'd throw the 1 hoping for the best.
That said, looking at the code, it doesn't look like detecting this is currently hooked up.