1)
Why does it say "Me'at b'Mispar"?
1.
Radak: [Those who will be exiled to Bavel] are few in number - 10,000.
2)
What is the significance of wrapping a little hair in the corner of his garment?
1.
Rashi: This refers to the few who will be exiled to Bavel and live. Radak - they will be guarded there until they return to their land, like something wrapped and tied in the corner of one's garment.
2.
Malbim: This refers to "Dalos ha'Am" (Yirmeyah 52:16) that Nevuzaradan left in Eretz Yisrael to be "Chormim v'Yogvim" (refer to Yirmeyah 52:16:2:1-2, 52:16:3:1-3) under Gedalyah's authority.
