27 According to the last instructions of David, the Levites were counted from those twenty years old or more.

Read 1 Chronicles 23:27 Using Other Translations

For by the last words of David the Levites were numbered from twenty years old and above:
For by the last words of David the sons of Levi were numbered from twenty years old and upward.
In accordance with David’s final instructions, all the Levites twenty years old or older were registered for service.