Here Oliver Cowdery made a scribal error in 𝓟 that he immediately caught and corrected. Earlier in this passage the text read “understand the things of the prophets”, so when Oliver came to the same “understand the things” a little further on in the verse, he followed the earlier phraseology by initially writing “understand the things of the prophets”. He then crossed out “the prophets”, supralinearly inserted “which were” (with no change in the level of ink flow), and continued writing the rest of the relative clause. Although the original manuscript is not extant here, Oliver’s corrected reading was undoubtedly the reading of the original text.
Summary: Maintain in 2 Nephi 25:5 the corrected reading in 𝓟 (“that understand the things which were spoken unto the Jews”).