Here's how I do QMOS on the myDevice.
1. Scan the item or search it to bring up it's page.
2. Tap the item name and scroll down.
3. Tap the "toss" option at the bottom.
4. Select why you're QMOSing the item and type in the quantity you're QMOsing into the available field.
5. Tap "toss" (I think. I don't have one in front of me right now) if you don't have any (more) scannable items to QMOS. If you have more scannable items to QMOS (maybe a "guest" left their grocery shopping behind because the lines were too long!) then scan the SAME item again. Now you can trash it and scan the next item, which will automatically be tossed! When you're done... tap "done," which is where "toss" was displayed before you scanned the first item a second time!
6. Curse the Target gods and pour out a venti dark roast for your fallen brethren.
Thanks
Deli ninja