Since the first stone contained the names of six tribes, it would have sufficed to write "ve'es Sh'mos ha'Nosarim". Why does the Pasuk add the word "Shishah"?
What are the connotations of the word "ke'Soldosam"?
Rashi, Targum Onkelos, and Targum Yonason: It means literally in the order that they were born 1 - Reuven, Shimon, Levi; Yehudah, Dan, and Naftoli on one, and Gad, Asher, Yisachar, Zevulun, Yosef and Binyamin 2 on the other. 3
Ba'al ha'Turim: Refer to 28:16:5:1*.
Da'as Zekenim #1: "ke'Soldosam" refers only to what is written just before it (the six names on the second stone), but not to those on the first one. 4
Da'as Zekenim #2: One opinion in Sotah 36a says that "ke'Soldosam" teaches us only about the spelling of their names - that they spelt 'Binyamin' with a second 'Yud' - as his father named him 5 - but not about the order of birth.
See Sifsei Chachamim.
Written Malei, with a second 'Yud' (as it was spelt when describing his birth (in Bereishis 35:11) so that there should be twenty-five letters on each stone (Rashi).
Hadar Zekenim: The problem with this explanation is that it clashes with what Rashi himself writes in Seifer Shoftim, 18:28, where, based on the Pasuk, he explains that the stone Leshem corresponded to the tribe of Dan, which is not the case according to Rashi here (See also Chizkuni).
Sotah, 36a: Because Yehudah was the first name on the stone. See Torah Temimah, note 2, who gives a number of reasons for this. Whatever the reason, the question arises as to why Yehudah was not also first on the stones of the Choshen. Refer to 28:16:5:1*.
See Oznayim la'Torah.
QUESTIONS ON RASHI
Rashi writes that they were in the order that they were born. But in Sotah 36a, all opinions agree that Yehudah was the first?
Refer to 28:10:1:3 & 4.