"(60) Apart from those Ancient Worthies who lived before the Covenant, but who were by God anticipatorily considered as in that Covenant, the first ones actually to enter the antitypical Ark—the Covenant—were Abraham and Sarah. Hence the antitypical Ark was first entered by the Ancient Worthies as a class in the persons of Abraham and Sarah in 2045 B.C. The last of all the classes to enter the antitypical Ark consists of the Youthful Worthies. They as a class first entered the antitypical Ark in 1881 1878, when the General Call ceased with the fulness of the Gentiles, and as a result the surplus consecrators became a class different from any other class."
This reference, taken out of context, could imply the Youthful Worthies became a class in 1881. There are a few reasons this is not possible. One, the very sentence itself tells us when surplus consecrators started to exist. We change it here to match the 1878 needs of the Executive Trustee. Two, this reference must harmonize with all of the other references in the same book. Three, the reference is fully explained on page 73.