Didn't she already do so (in flashbacks before his moves)? And the aim of the match is to impress Tengan Kako, so making him have a handicap at the start is one things on the plan. Moreover, he don't know anything about the game, so telling him which sets to get ready for (which is much more complicate to remember) is not as effective as giving hints where he can use the imagination of complete newbie to create chaos. And don't forget mahjong is very complicate, the structure is 4 rounds 16 games for a normal play, nearly impossible to remember all the moves, especially for complete newbies like him.