AR15

The most surefire way to know if you are opening or closing is to fully turn the adjustment to handtight. When fully closed it will not cycle a new round at all. On an AR-15 the procedure is to fully close the gasblock, then fire one round from a one round loaded magazine, then open the gasblock by one rotation, then load a single new round in a magazine and fire again. Repeating until the rifle locks back to the rear on the empty magazine. Getting enough force to lock back shows it is cycling enough. Then open by an additional 1/2 turn, for a little bit of wiggle room to account for slightly underloaded rounds or fouling. You don't want to just open it all the way as a brute force solution to get it cycling, since that will cause excessive wear and tear on parts.

I presume the procedure will be the same on an AR-10.

If you get the gas dialed in where it is just enough to properly cycle, then I wouldn't worry too much about where the brass is going as long as it isn't interfering. Cycling is a better metric than trying to eyeball brass flight time. Some rifles send brass into orbit.