No one can tell the actual number, but for sure there are hundred of thousands of Christians that died in the first century for Christ, not to mention also those who died from natural courses.
That means the number should be millions.
The number 144.000 is symbolical,and the book of Revelation is a symbolic book. The ignorance of the GB and the fact that they don't know Greek the language that the New Testament was written, has led them to be the most rediculous religion group in the world today.
Revelation chapter 19 verse 1 clearly says: And I heart the voice of a great multitude in HEAVEN.
So they are in heaven and NO one can challenge this!!!