A literal reading of the entry for cyber leg jacks is a little confusing.
You have to have two legs to take the jacks, but it seems that each leg has its own rating. So does that mean that if I have rating six in each leg that I then have 12 additional dice for those tests and can fall even further?

Or you could put rating 1 in one leg, rating 6 in the other, and do really enormous cartwheels...

I think both jacks have to have the same rating and that single rating is what you add to your jump pool. Note that the reason they specify the rating per leg for capacity is because the cost is for both jacks together.