Almost certainly the value of pensions. There are teachers on that list making $65k with "benefits" of 1mm, which is probably the NPV of ~20 years of pension income.
Doesn't seem to add up though, if you keyword search for "teacher" [0], the results are dominated by GCC with consistently elevated benefits. Once you get out of GCC dominated results, the numbers start looking a lot less surprising - until another GCC entry shows up.
My completely uneducated guess is that GCC reports the entire value of the DB pension as "income" for that year, whereas all other institutions correctly report just the increase in value.
[0] https://transparentcalifornia.com/salaries/search/?q=teacher