The Pasuk says:
וְאֵת כָּל הָעֵדָה הַקְהֵל אֶל פֶּתַח אֹהֶל מוֹעֵד – And assemble the entire community at the entrance of the Tent of Meeting.
on which Rashi writes:
הקהל אל פתח אהל מועד: זה אחד מן המקומות שהחזיק מועט את המרובה – Assemble [the entire community] at the entrance of the Tent of Meeting: This is one of the instances where a small [area] accommodated a large [number of people]. — [Lev. Rabbah 10:9]
The Panim Yafos wonders what’s going on here. The courtyard to the Mishkan was 100 x 50 amos, half of which was behind the entrance, so to have been at the entrance, the entire male population of Jews aged 20-60 (603k + 22k Levites) had to fit into an area of 50 x 50 = 2,500 square amos. A person takes up 1 square cubit standing up, and 4 cubits to bow down, which they did. if 625k people needed 4 amos each, then really they needed an area of 2.5 million to congregate in, and yet the Pasuk says they fit into an area 0.1% of the size needed. (2,500 into 2.5m goes 1,000 times).
What’s going on? The Panim Yafos explains:
In the Midrash Rabbah of Toras Cohanim, R’ Meir says that ה אֱלֹהֵי אֲבוֹתֵכֶם יֹסֵף עֲלֵיכֶם כָּכֶם אֶלֶף פְּעָמִים וִיבָרֵךְ אֶתְכֶם – May the Lord God of your forefathers add to you a thousandfold.
2.5k x 1k = 2.5m!