Hi, dhwachs!
Welcome to Gadgets!
First off, I've learned long ago (another time and place in my life) that for every one person who has a question, there are 3 or more that are just too afraid to ask it. So, thank you for being brave enough to ask!
Secondly, even though I don't have the Superwave, I have a convection oven/microwave in our camping trailer and I remember when I first got it I was totally confused about the rack system.
Maybe my experience will work for you too?
Here's what my problem was:
Way back in my toddler years I learned to stack blocks with the largest block on the bottom and the smallest blocks on top.
So, the first time I looked at the mess of racks for my RV Conv/Micro oven I immediately tried to stack them with the little rack on top. Of course, the little rack promptly fell through the holes in the large rack and ended up all topsy-turvy in the microwave. (Thank goodness I didn't have food on it yet!

)
So, then I played around and around with it until I was nearly too frustrated to cook. I just started using one rack at a time, until I had to bake cookies.
Okay.... let's just say that my idea of "camping" food is nothing like our friends' ideas or the traditional recipes. I act like we're eating exactly like we do at home, but with more free time to cook!
So anyway, now I want to use both racks to bake more than 3 cookies at once. By this time though, I had used both racks alone at least a few times, and as I realized I needed both at the same time, it dawned on me that the smaller rack sits nice and close to the bottom of the oven, but that tall rack always seems so high in the air!
My childhood OCD about having my building blocks all stack up in descending order started to kick in, but I squashed it and set the small rack in the oven on the floor and then set the large rack in over the top of it. I did rotate them so that the legs and the wires were all going in the opposite directions (maybe considered "criss-crossed"?) and then I was able to bake two trays of cookies at the same time!
Like I said above, I don't know if this is what the Superwave looks like, or if you're going to read this and think I'm about the wackiest person you've ever heard, but it is definitely the instance that pops into mind when I read your post. I do hope it helps you, though!
*Tink
ETA: Okay.... so after all that, I re-read your post and see that your instructions actually say to put the little rack on top!
You have my express permission to relieve your anxiety over this situation, by laughing at how dumb I am!
I must have read that before I had enough coffee in me yet.
