Enchanting glitch

Okay, I had a book with multiple different enchants on it, some for armor some for sword and some for bow, I was trying to get sweeping edge for my sword, which had 6 enchantments on it already. Well when I enchanted my sword, it did enchant with sweeping edge but it also got the enchant Flame (for bow) as well as Fire Protect 3 (for armor) so just letting you guys know.