I guess another check on your 'dipstick' is if you put the proper volume of oil in the engine after giving her a good draining, you should have had an exactly full reading on the stick. Anything otherwise, then you have either the wrong dipstick, incorrect volume of oil, or a non-stock filter or oil pan.

And you said before there are no leaks, right? Like from a crack in the oil pan that is only reached when the oil leve is topped off?

Either way, something funny is going on. But good old 'process of elimination' should do the trick in the end.

Brian