Where does the "lumbar support" on my chair go?

I got one of those neat Herman Miller Aeron chairs off eBay for a couple hundred bucks, and it comes with a moveable lumbar support. What am I supposed to do with this thing? I can get it as low as my waist or as high as my shoulder blades. What is the most healthful place to put it? Is using the lumbar support supposed to be more comfortable, or does it simply promote better posture? I’m young and have many years of chair-sitting ahead of me :smack: , so I’ll put up with some minor discomfort if it means not screwing up my lower back.

One would assume it should be positioned near the lumbar vertebra.

I suppose so, but it sure feels funny having this thing stuck in at an angle around there