I feel kind of dumb asking this, but I can't figure out my new Ortlieb map case. This is apparently the latest model that anchors in front and has an adjustable cord to the rear of the handlebar bag. So I have it mounted per the instructions, roll top forward, cord routed exactly as instructed. What I end up with is a doubled over transparent map case measuring about 5" x 11", and not sure how to access the folded under bottom half.

So how is this case intended to be used, what's the purpose of the adjustable cord setup, and is the front attachment intended to be quick-release? I like Ortlieb stuff but this just baffles me. Thanks for any insights.