Possible defect in my Invisalign tray? (photos)

I'm supposed to put my 3rd set of trays in tonight and when I got them out of the package I noticed what looks to be a possible defect. There is an extra line of plastic on the very back molar space. I'm not sure if it's a defect or if it's supposed to be there for some reason? It wasn't on any of my other trays and I'm worried that it's going to keep my tray from fitting properly. I do plan on calling my dentist but the office isn't open today. Can anyone help?