Don't worry Sea Breeze, I looked it up. Seems like they view the broken off branches as the natural Jews and the wild branches as the 144,000. But then they still have the problem with the remnant of natural Jews that is going to be saved. Sometime in future these will be regrafted to the tree because of His promises to their forefathers.
So this is how I see it: Natural branches (Jewish remnant) + wild olive branches (Christians) = All Israel, i.e., the Israel of God (Rom. 11:25, 26; Gal. 6:15, 16).
According to the Watchtower: What do the various features of the symbolic olive tree represent?
The tree: the fulfillment of God’s purpose regarding the Abrahamic covenant
The trunk: Jesus, the principal part of Abraham’s offspring
The branches: the full number of the secondary part of Abraham’s offspring
The “broken off” branches: natural Jews who rejected Jesus
The “grafted in” branches: spirit-anointed Christians out of the nations
As foretold, Abraham’s offspring—Jesus and the 144,000—will bring blessings “to people of the nations.”—Ro 11:12; Ge 22:18