According to the PRD:
Bomb: On a direct hit, an alchemist's bomb inflicts 1d6 points of fire damage + additional damage equal to the alchemist's Intelligence modifier. The damage of an alchemist's bomb increases by 1d6 points at every odd-numbered alchemist level (this bonus damage is not multiplied on a critical hit or by using feats such as Vital Strike). (Emphasis: Bold)
What exactly is the bonus damage the parenthetical text is referring to?
- The Intelligence Modifier added to the bomb?
- The Increase in Damage by die/level?
- The Splash Damage dealt?