What's the meaning of this clause from the constitution?

"No Capitation, or other direct, Tax shall be laid, unless in Proportion to the Census or enumeration herein before directed to be taken."

I understand a capitation is being used interchangeably for direct tax, but what does it mean when it says "unless in proportion to the census or enumeration herein before directed to be taken."? According to the dictionary, herein means "within this document, within this text, or in this matter" and it makes no sense in this context. Census and enumeration in what matter? And the last part "before directed to be taken" doesn't even sound grammatically correct. Maybe it's just archaic english but I would really appreciate it if someone could help explain this to me

Article ! Section 2 of the Constitution directs the Enumeration (actual count) of the population for the purposes of taxation and representation in the Congress.

https://usconstitution.net/xconst_A1Sec2.html