The 01. April 1986 Watchtower states:
“Approved association with Jehovah’s Witnesses requires accepting the entire range of the true teachings of the Bible, including those Scriptural beliefs that are unique to Jehovah’s Witnesses. What do such beliefs include? [...] That only 144,000 Christians will receive the heavenly reward. (Revelation 14:1, 3)
The 1995 WT refutes their own WTS doctrine re: only 144 000 going to heaven.
8 When Israel rejected and killed His Son, Jesus Christ, God finally rejected her. So no longer was that Jewish nation a figurative wife to Him, nor was He the Father and Teacher of her wayward sons. (Matt. 23: 37,38) However, Israel was only a typical, or symbolic, wife. The apostle Paul quoted Isaiah 54: 1, which speaks of a "barren woman" who is different and distinct from "the woman with the husbandly owner," the nation of natural Israel. Paul reveals that anointed Christians are children of the "barren woman," whom he calls "Jerusalem above." This antitypical figurative woman consists of God's heavenly organization of spirit creatures. -- Galatians 4: 26,27. (wt95 08/01 page 11 paragraph 8)
The scripture thus indicates (using the WTS' own interpretation of the 'women') that the number of anointed Christians exceeds that of fleshly Israel. The cumulative number of natural Israelites between the Exodus and the coming of Christ Jesus was in the many tens of millions; therefore, many more than 144 000 are spirit-anointed Christians.
I hope this helps.