There are actually two errors commited by Adam I see in this situation:
1/ Failure to Resolve
Archangel of Thune's triggerred ability properly
2/ Resolving the ability ahead of time - it only triggers after
Sphinx's Revelation resolves
They were both made at the same time.
Since he didn't anounce value of X for Revelation and put 3 counters on the angel (instead of 1), we should assume the “X = all mana in mana pool” shortcut is in order. He failed to draw the cards and note change of his life, so he clearly resolved Archangel's trigger before he was entitled to.
Gaining life, unlike drawing cards, is a one-time event. Adam doesn't gain 3x1 life, but simply 3 life. Therefore he should have put only one +1/+1 counter on his creature.
GRV for Adam, no infraction for Netta (called a judge immediately).
As for the fix, it's rather simple. I'd rewind by taking counters off the Archangel and leave
Sphinx's Revelation with X=3 on the stack (it had been played properly, so no infraction here).
Warning for Adam.