Should There Be Multiple Trays with Same Number on Them?

I just finished my first trays. I put on my second tray and then got curious about what the next two sets (3&4) looked like. Each package is marked U & L 3 & 4 but the trays inside are both marked U & L 2. I even tried on what should have been the 4th set and the feel just like the ones I'm currently wearing. This must be a mistake right? I am going out of town and want to be sure I have the correct trays with me.