Here’s an excerpt from one of my books on Exodus 28…I think it helps give perspective to cryptic readings:

THE PRIESTLY GARMENTS God prescribes (Ex. 28) are strange and colorful. Perhaps some of the details were not meant to carry symbolic weight, but were part of the purpose of the ensemble as a whole: to give Aaron and his sons “dignity and honor” as they discharge their priestly duties (28:2, 40).
Some of the symbolism is transparent. The breastpiece of the high priest’s garment was to carry twelve precious or semi-precious stones, set out in four rows of three, “one for each of the names of the sons of Israel, each engraved like a seal with the name of one of the twelve tribes” (28:21).

The breastpiece is also called “the breastpiece of decision” (28:29). This is probably because it carries the Urim and Thummim. Perhaps they were two stones, one white and one black. They were used in making decisions, but just how they operated no one is quite sure. On important matters, the priest would seek the presence and blessing of God in the temple, and operate the Urim and Thummim, which would come out one way or the other and thus, under God’s sovereign care, provide direction. Thus over his heart the priest simultaneously carries the names of the twelve tribes “as a continuing memorial before the LORD,” and the Urim and Thummim, “whenever he enters the presence of the LORD,” thus always bearing “the means of making decisions for the Israelites over his heart before the LORD” (28:29–30).

On the front of his turban, Aaron is to affix a plate of pure gold. On it will be engraved the words, “HOLY TO THE LORD” (28:36). “It will be on Aaron’s forehead, and he will bear the guilt involved in the sacred gifts the Israelites consecrate, whatever their gifts may be. It will be on Aaron’s forehead continually so that they will be acceptable to the LORD” (28:38). This assumes that the “sacred gifts the Israelites consecrate” were primarily sin offerings of various sorts, offered to atone for guilt. The priest, even by the symbolism embodied in his garments, conveys this guilt into the presence of the holy God, who alone can deal with it. The text implies that if the priest does not exercise this role, the sacrifices the Israelites offer will not be acceptable to the Lord. The priestly/sacrificial/temple structure hangs together as a complete system.

In due course these meditations will reflect on passages that announce the impending obsolescence of this system, which thereby becomes a prophetic announcement of the ultimate priest, the ultimate covenant community, the ultimate authority for giving direction, the ultimate offering, the ultimate temple. There is no limit to his “dignity and honor” (cf. Rev. 1:12–18).
-D. A. Carson, For the Love of God : A Daily Companion for Discovering the Riches of God’s Word. Volume 1