I don't understand rating as weighted by the amount of something. I mean, there are monster that have the ability to swallow whole and inflict damage. You only need a single round.
G: The giant frog gobbles Bobbie. You loses 2 HP.
PG: The giant frog gobbles you. Despite not having teeth, the monster has a dangerous drool that creates burns. You loses 2 HP.
PG-13: The giant frog gobbles you. Everyone, you no longer see your friend, but you can hear screams from inside the stomach of the giant frogs. Bobbie, digestive acids are slowly dissolving your flesh. The pain is intolerable, like a thousand needles, and you hope help will come soon. You loses 2 HP.
R: Everyone, The giant frog gobbles Bobbie. Noone have ever survived such a fate for long. Even though there are stories of other fighters acting quickly enough to rip open the frog's belly, freeing their friend from dying, the acid is often very quick to act and the scarred husk of a person they could release was often lacking a limb, or eyes. Eyes are often the quickest part of the body to dissolve, unable to resist the potent acid of the beast's belly. Only the most potent magic can then save the victim, as often it is fully immersed in the digestive acids ; simply washing the survivor after the fact isn't enough to solve the slow melting of the lungs, if he wasn't lucky enough to hold his breath during the whole ordeal... one can't simply endure without a shriek. More often than not, death occurs by suffocation over the course of an agony over several days. Maybe if you're quick enough, you'll be able to give your friend a merciful death. (btw, turning to Bobbie's player, deduct 2HP).