Oil Weirdness

So I changed my oil about a week ago. I'm not leaking oil or "making" oil
(meaning, no blown gaskets or anything). I changed the oil and filter
and carefully added oil until it was full. I had done the filter as well.
For the record, I know how to do an oil change properly.

I drove it for a day and decided to check the oil for my own peace of
mind and discovered it was over-full. I jacked the car up and let some
out. A little too much so I added until she was full again. Drove it and
got the same thing. I did the drain thing today one more time and now
she's cool..even after a day of driving.

But what causes this? Is there an area that holds oil that I don't know
about? Really weird.

Again, my engine is tip-top. No leaks, No seal leaks, no blown gaskets.
She doesn't "make" oil...or even burn it.