Hello Akvan,
- We can think of it this way. Nibbana is attained in four steps (Sotapanna, Sakadagami,..). At each step one comprehends Tilakkhana (and asubha nature) to a significant level. Magga citta is basically when one really grasps this “real nature” at a given level, and that is completing a kamma. One gets the vipaka (or the result of that kamma) in the very next citta.
– This is a citta niyama (a universal law). All four “lokottara kamma” have immediate results, in the very next citta. - Sotapanna Anugami has not yet attained a magga or a phala citta. He/she has heard the correct Tilakkhana and may have some understanding. But that understanding has not yet reached the “tipping point”; see, “Sotapanna Anugami and a Sotapanna“.
- The citta vithi for a magga phala is discussed at the end of the post, “Citta Vithi – Processing of Sense Inputs“:
B B B “BC BU MD P U A G Pa Fr Fr” B B B
In other words, a Sotapanna Anugami is getting closer to the “change of lineage” or G. The earlier stages of P, U, A, may be reached gradually. Once that level of comprehension is complete, one makes that transition (G), completes the lokottara kamma, and immediately receives the phala.