What is their Isur to shave the head?
Rashi: They may not remove all the hair.
What is the meaning of "u'Fera Lo Yegalechu"?
Rashi: They will not grow their hair long [Radak - more than 30 days growth].
What is the meaning of "Kesom Yichsemu Es Rosheihem"?
Rashi citing Menachem: Like Kosemes, which is arranged on the sheaf ? the head of one [seed] is at the root of another. Radak ? so it says in Sanhedrin 22b [regarding the Kohen Gadol's haircut]. Malbim ? also in this way they will resemble a Kohen Gadol.
Radak: It is an intermediate measure ? the head is not totally shorn, nor is the hair long. Rather, it is moderate length.
Radak citing Targum Yonasan: They will cut the hairs of their heads.