Number of short hairs coming out of the base of the head Tefillin

Question

Shulchan Orech 32:44 discusses the hair which is used to bind the parchments in the Tefillin.

Rav Moshe Isserles says: "the custom is to bind hair on the parsha and then bind on that kosher parchment and then bind on that hair. And the custom is to use calf-hair and if one doesn't find calf-hair then one uses cow or ox hair and one washes the hair very well so that it is clean. Some of this hair should be seen outside the Tefillin-boxes."

Rav Aryeh Kaplan in "Tefillin" in the beginning of the chapter "By a Hair" says that there are four hairs which come out of the base of the head-tefillin. [for Rashi tefillin] Does anyone know his source that there should be specifically four?

The commentaries that I saw seem to discuss the length of the hairs and the location of the hairs, but not the number.

I looked at my own Tefillin and there are indeed four hairs. But I looked at other people's and there seem to be differing numbers of hairs.

Answer 1

Rav Chaim Kanievsky was asked this in Daas Noteh pg.298. He was asked if one needs to be makpid to davka leave out one hair and not more since the Shulchan Aruch uses the language of hair and not hairs. Rav Chaim answered there is no kapeida,and one can do more and in fact the minhag is for the Sofrim to put more out. So from the strict reading of the Zohar which is source for this one hair is what is written .

The Zichron Eliyahu seems to hold that it is correct to have both the hair wrapped around the parsha and the hair wrapped around the klaf (which is around the parsha) to stick out so that will be more than one hair.