It says on Rashi beginning of Acharei https://www.chabad.org/dailystudy/torahreading.asp?tdate=4/18/2021
with this: בְּזֹאת. Its gematria [numerical value] is 410, an allusion to [the number of years that] the first Temple [would stand when the kohanim were righteous like Aaron, and it was as if Aaron lived all these years and entered the Holy of Holies]. - [Vayikra Rabbah 21:9]
בזאת: גימטריא שלו ארבע מאות ועשר, רמז לבית ראשון:
The question is, Rashi in general said that he's only coming to explain the simple meaning of the verses, like he says in Bereishis 3:8 https://www.chabad.org/library/bible_cdo/aid/8167/showrashi/true
And they heard: There are many Aggadic midrashim, and our Sages already arranged them in their proper order in Genesis Rabbah and in other midrashim, but I have come only [to teach] the simple meaning of the Scripture and such Aggadah that clarifies the words of the verses, each word in its proper way.
וישמעו: יש מדרשי אגדה רבים וכבר סדרום רבותינו על מכונם בבראשית רבה (יט ו) ובשאר מדרשות ואני לא באתי אלא לפשוטו של מקרא ולאגדה המישבת דברי המקרא דבר דבור על אופניו:
Rashi already told us towards the beginning of his commentary that his only purpose is to explain the absolute simple meaning, or at least those midrashim that are relevant in explaining the simple meaning of the verses, based on what Rashi said earlier, it wouldn't seem like his purpose is to bring allusions, in the world of remez, hints, when he already said that his job is only on the simple meaning, pshat (or at least hints and midrashim etc that would explain the simple meaning of the verses etc.)
So why does Rashi find the need to bring here an allusion and gemateia of the word בזות? Why didn't he suffice with simply continuing on into the next part of his commentary?
True, it's a midrash, but Rashi doesn't bring every midrash, so why did he bring this one, especially since it has to do with merely a hint and numerical value, how is this relevant to the simple meaning of the verse?