1st& 2nd ed had the base xp for defeating a monster plus + some amount based on it's hit points. It read something like 4000 +3/hp. If the monster had 50 hp then you should award a total of 4150 xp for that monster.This is similar to mine. A friend told me that when he first started playing AD&D1, he thought that characters gained the HIT POINTS of the monsters they killed (added to their own HP total, of course). The cure light wounds spell suddenly became much more useful once they realized their mistake.
However, the first time I read this as an 8 year-old, I thought this meant that you award 4000 xp and the character whom killed it would get 3 hp.