12 minutes
Make sure the rear foot is elevated to something smaller than knee-height and that your front foot is 3-3.5 paces out from the box/bench. The front shin should be vertical and your weights should not touch the floor for the entire set. If they touch the floor, you are leaning forward too much. Take the time to get good with the movement and get good work out of it. You're looking for glutes on this one.

12 Min Cap
Scale so that the double unders can be done in less than 1 minute. The 50 ft OHL should be on your weaker side for Round 1 the whole length. Each round you'll alternate arms and finish the last round with your weaker arm so that you've done more work on your weaker side to help get more balanced.

Use a light weight and go for a burn. We're aiming for quads here so if you can narrow your stance and/or elevate your heels, go for it. Minimize the rest between sets. If you chose too light a weight or can't handle the bar in your arms well, go for 50 unbroken.