This chart is from Pickering's Appendix G to his book, The Identity of the NT Text II, online. It is based upon W.G. Pierpont's careful check of von Soden according to a personal communication from Pierpont to Pickering. He presents 33 variant sets (units). Sometimes the % totals exceed 100% because Pickering has rounded to whole numbers. Pickering mentions that Groups M1-M4 are frequently internally divided, and their MSS often 'go astray' with a variety of added variants which are not recorded on the chart.
Pickering uses [ ] brackets for (1%-20%), and ( ) brackets for 21%-95%, and whole numbers for 95%+.