Or HaChaim on Exodus 28:36/אור החיים על שמות כ״ח:ל״ו

1 קדש לה׳. "Holy unto G'd." This means that as long as the words "Holy unto G'd" appeared on the headband (golden plate), this was acceptable. When the Talmud said in Shabbat 63 that the words were arranged in two rows, this means that the name of י־ה was engraved on top and the word קדש followed by the letter ל underneath. Such an arrangement of the words was not mandatory. You will find there that Rabbi Eliezer son of Rabbi Yossi reported that while in Rome he personally had seen the ציץ which the Romans had captured, and that the words "Holy unto G'd" were engraved on it in a single line. This proves that the order in which the words were engraved did not matter. When Maimonides wrote in chapter nine of his treatise on Kley Hamikdosh that the words appeared in two rows, with the word קדש in the second line, this does not present a difficulty. He referred only to the preferred way of engraving these words.