Math doesn't math

I feel like number of riders they say die in this book doesn't match the number of riders the college graduates each year. I also feel the number of people killed within the college is more than they get killed in battlefield . Violence within the college seems forced and doesn't make logical sense when they have an enemy province to defend. This Violence within the college would make more sense if it was a reality show or individual ranking event , not when they have a more dangerous common enemy to face . At this rate of Violence they gonna destroy themselves. Just my thoughts.