וְאֵת֙ פְּדוּיֵ֣י הַשְּׁלֹשָׁ֔ה וְהַשִּׁבְעִ֖ים וְהַמָּאתָ֑יִם הָעֹֽדְפִים֙ עַל־הַלְוִיִּ֔ם מִבְּכ֖וֹר בְּנֵ֥י יִשְׂרָאֵֽל׃
And as for the redemption of the two hundred and three score and thirteen of the first-born of the children of Israel, that are over and above the number of the Levites,
Read kabbalistic (mystical) interpretation of Numbers 3:46: and classical mystical sources.