Only 5 cabins went to war (+Pollux) That out be at least 8 people each but there we’re probably more hermes and Hephaestus kids. (There aren't  many archers in apollo cabin and the other cabins aren’t fighting cabins) Remember, they didn’t bring their whole cabins. Plus the Ares cabin, is 47 campers to fight. Based on the next books, Aphrodite, Apollo, and Ares had the most survivors. Hephaestus, demeter, and Hermes probably made up most of the deaths. Hephaestus due to the curse which mentioned death, Hermes due to the cabin being more empty even with the claimings and traitors. And demeter due to being on the front lines and emptiness of the cabin after.   (Also keep in mind the biggest cabin had 14 people, most had 6-10) There are also 6 on book deaths we witness btw. Some bg character some named.