'Twenty' in the Bible

These were the sons of Levi according to their fathers’ households, even the heads of the fathers’ households of those of them who were counted, in the number of names by their census, doing the work for the service of the house of the Lord, from twenty years old and upward.

For by the last words of David the sons of Levi were numbered from twenty years old and upward.

But David did not count those twenty years of age and under, because the Lord had said He would multiply Israel as the stars of heaven.