Chess.com's Flagging Rules

I just had a KNNP vs KN position, in which I had the KNNP and my opponent had a KN. He took my pawn, but I then proceeded to flag him, not knowing how the game would end.

Are there some concrete flagging rules I can read up on somewhere?

I've posted a screenshot of the position (and proof of win via flag) below. I had a pawn on h3 that was taken by his king. 

Link to the game is here: https://www.chess.com/game/live/24982266117

It says you won.

Are you complaining because you think it should have been a draw?

Not complaining! Just confused as to what the rules are. I'd like to know for the future.

#1
FIDE Laws of Chess:
"6.9      
Except where one of Articles 5.1.1, 5.1.2, 5.2.1, 5.2.2, 5.2.3 applies, if a player does not complete the prescribed number of moves in the allotted time, the game is lost by thatplayer. However, the game is drawn if the position is such that the opponent cannot checkmate the player’s king by any possible series of legal moves."

https://handbook.fide.com/chapter/E012018 

The Laws of Chess are not implemented correctly, because it is too hard for software to determine if there is a series of legal moves that leads to checkmate or not.

The rules the site uses are explained in the following:

https://support.chess.com/article/268-my-opponent-ran-out-of-time-why-was-it-a-draw

https://chesscom.helpscoutdocs.com/article/128-what-does-insufficient-mating-material-mean

Because of the complexities involved Chess.com simply calculates based on removing all of the opponents pieces (keeping the king) and seeing if checkmate is possible.  Thus if a player with K+N has a forced mate against a flagging opponent (win in both FIDE and USChess) Chess.com will give a draw and if White with only Ke1, Be2 and pawns a4, c4, e4, g4 flags Black with only Ke8, Be7 and pawns a5, c5, e5, g5 then Chess.com will give a win while both FIDE and USChess would give a draw (checkmate with legal moves is not possible even with all of the [blocked] pawns/bishops on the board).  The OP's K+2N vs K+N is another example of a difference between Chess.com and US Chess since that would be a draw in US Chess (if there was no forced win) while Chess.com and FIDE allow it to be a win.

K+2N (vs K with no pawns), K+N and K+B for the non-flagging player are the difference between FIDE and US Chess.  With those specific sets of material for the unflagged player US Chess requires a forced win to win on time while FIDE only requires a possible win (including a helpmate).

To sum up,  Chess.com follows US Chess rules a bit more closely than FIDE rules but does not fully follow either.

Thanks so much for the explanation, folks!