Is there anything you think I should know?

I'm taking a class on machine quilting at the Pacific International Quilt Festival. I've got all the of the supplies and will be doing the required cutting before the class. I'm not entirely sure what they mean by needing a "machine with tray," though. I've posted about it before and emailed the show, they have no idea and said they'd ask the teacher, but not response yet!

I hope I can navigated the convention center okay with my sewing machine in one hand, my notions box in the other, and a backpack full of supplies!

(not sure how to change the name of the topic, but I meant to say that I'm taking the class on Saturday, not tomorrow haha!)