If you want a 10 Yr Notes to 30 Yr Bond to Ultra Bond Butterfly, simple overlap the leg quantity ratios.
The June '20 CME ICS leg quantity ratios for the NoB are 5:2, and for the BoB are 2:1. So, for June '20, the correct 10's-30's-Ultra Butterfly leg quantity ratios would be: 5:4:1. You are...