This sentence is a bit sneaky, and I almost deleted it. The accusative plural of ābra is ābrī. This happens to be identical in form (though not in pronunciation) to the nominative plural conjunctive form of ābra. Technically you haven't learned this form yet, and have only seen it used in a different way. Even so, since the form exists already at this stage, it's available to be used, and so one of my contributors made a sentence with it.
I have since updated the notes on the skills to make it clear that this is an accusative plural form. My apologies that I hadn't realized this until now. I hope this change helps for the future. If not, I will delete this sentence.