Using your example, you would (prior to the statement date) pay off the $850 and pay the $500 down to somewhere between $1 and $45. However, if you aren't applying for anything, this level of attention isn't required. Make sure you're paying off each card in full every month. Then, try to get each card to below 9% utilization. It's okay if you go over again, because utilization is measured at a moment in time and has no memory, so if you pay it down again, it will be as if the increase in utilization was never there.
Addtionally, don't let the statement cut with both cards at $0. That makes it look like you're not using credit, which can have very bad effects on your score.
