That's the size of the cut (in millions) that UC is being required to take with the Governor's new budget, with possibly another $100 million if the optimistic revenue projections built into the budget do not materialize. (CSU and CCs will also get similar reductions – the Governor's budget includes almost 12 billions in cuts to services.)
Having averted the worst-case scenario (a total reduction of $1 billion to UC), there is a temptation to sit back and enjoy the summer. But in fact (unless I am mistaken, I didn't check) $650 million is the largest cut the University has been required to take in a long time. Did Arnold ever do anything remotely approaching this?
Of course the Regents have announced that any reductions above the $500 million in the January budget will come from tuition increases. So the UC faculty can sit back, take it in stride, tell each other there is nothing they can do, and that this, too, will pass.