Question: What happens if someone has the incorrect number of tiles after the Charleston.

Answer: At the end of the Charleston, everyone should verify they have the correct number of tiles. If a player has the incorrect number of tiles, the hands are thrown in and a new game would begin. However, there is one exception to this rule. If the player to the left of East is short one tile, that player may take their 13th tile since that tile is rightfully theirs. This can only be done prior to East discarding their 14th tile.

Source: Mah Jongg Made Easy 2024, page 14, bullet #9