In the Minhagei Yisrael article I quoted in my answer to Versions of HaNeros Hallalu, Rabbi Sperber notes that this is found in the version of the Rosh.
He suggests that it may have been added to support the opinion in the Gemara Shabbos that listening to the Rabbis' Chanukah Mitzvos (and saying Asher Kideshanu Bemitzvosav Vetzivanu) is supported by the verse of "Lo Sasur", which seems like a commandment (mitzvah), as opposed to the other opinion there, that it is derived from "She'al Avicha", which sounds more like it is optional. He further notes that the Yerushalmi's version of the Bracha is Vetzivanu Al Mitzvas Hadlakas Ner Chanukah.
Basically, it would mean and all the 8 commanded days of Chanukah, but it is awkward grammar.
In his words: