callsYou can never call a discard for a mere pair. The only pair you can claim is the one that completes your mahjong.

callsCalling kills a hand marked C. Check the letter twice, call once.

callsA call skips every player between you and the discarder. Sometimes the tempo theft is worth more than the tile.

callsExposures can be corrected only until you discard. Verify the group before you let the next tile go.

callsThe later you call, the more your exposure says. Early calls blend into the noise; late calls read like a declaration.