Pry the arm off the spindle and reposition it a couple of teeth in they direction you want it to stop. There are usually around twenty teeth on the spindle so you can really fine tune the adjustment relatively easy.
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If the wipers don't touch the glass on the bottom half of the wiper blade. I would make sure they are the right type. I found the s part of the wiper arm touches the bottom side of the wiper assembly...
GM will say it's a safety feature. Not true - notice that the bottom part of your door is curved in to make space for the wheel well which doesn't allow room for the window to roll all the way down....