Were the 120 disciples the total number of believers in Jerusalem after Jesus' ministry?
The 120 men were likely the total male believers in the Jerusalem area after Christ's three years of earthly ministry, not counting the women. This was presented as a cautious estimate rather than a firm doctrine, and the passage explicitly says there were 120 men besides the women.
Les explains that he makes this comment cautiously and tends to think the 120 men were all the believers in the area of Jerusalem after three years of Christ's earthly ministry. He notes there were also women, but of the men there were 120. He says that after three years of Christ's earthly ministry in the immediate environs of Jerusalem, this was the sum total of His fruit. He does not hold the point strongly and says to take it for whatever it is worth. The text then shows Peter moving to fill the twelfth slot because the Kingdom was still at hand.
And in those days Peter stood up in the midst of the disciples, and said, (the number of names together were about an hundred and twenty,)
More Questions
How many true Jewish believers were there in Jerusalem after Jesus' three-year ministry?
The 120 believers gathered at Pentecost were, in Les's view, the sum total of true Jewish believers in the Jerusalem and Judea area after three years of Jesus' ministry.
How many believers were gathered in the Upper Room in Jerusalem after Jesus' resurrection?
By the end of Christ's three-year ministry, after His crucifixion and resurrection, the believers who gathered in the Upper Room in Jerusalem numbered about 120 names, and Les thinks that was all there were in the Jerusalem area (though not necessarily all in northern Israel).