User blog comment:KouChisato/Post-Suzuki & Tamura Seniority/@comment-131168-20160601183255

51 people listed, making the seniority mid-point #26 Nonaka Miki. It also means a full third of members, 17, joined in 2015.

Though actually, both of those are off a little bit--looks like Niinuma Kisora is missing from the Tsubaki Factory section.