Penance brand with Runebinder removes only one brand after the explosion

Penance Brand description states, that when the branded target reaches 20 energy "a large explosion occurs and the brand is removed". This seems to imply that once the explosion occurs, all brands should be removed from the branded enemy. However, when using Runebinder and attaching two brands to an enemy, only the first brand is removed after the explosion (resulting with two explosions from two brands). The range of explosion also varies greatly depending on when is the brand applied.