These were the orderings of them in their service to come into the house of the Lord, according to their manner, under Aaron their father, as the Lord God of Israel had commanded him. (1 Chronicles 24:19)
That is, according to the specific order that had been fixed by Aaron. Each of the 24 classes took its turn in rotation, for the carrying out of the services in the house of the Lord.
The orderings of them.
That is, the numerical order established for their ministerial services in the house of the Lord.