Then they gave lots to them, and the lot fell upon Matthias, and he was counted with the eleven apostles. When the time for Pentecost was fulfilled, they were all in one place together.To my eyes, this says that the twelve were together and implies nothing more. But I understand if you disagree.
I understand where you are coming from but look at how the verses flow:
Act 1:13 And when they were come in, they went up into an upper room, where abode both Peter, and James, and John, and Andrew, Philip, and Thomas, Bartholomew, and Matthew, James [the son] of Alphaeus, and Simon Zelotes, and Judas [the brother] of James. These all continued with one accord in prayer and supplication, with the women, and Mary the mother of Jesus, and with his brethren. 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,) Men [and] brethren, this scripture must needs have been fulfilled, which the Holy Ghost by the mouth of David spake before concerning Judas, which was guide to them that took Jesus.
Act 1:21 Wherefore of these men which have companied with us all the time that the Lord Jesus went in and out among us,
Act 1:23 And they appointed two,
Act 1:24 And they prayed, and said,
Act 1:26 And they gave forth their lots;
Act 2:1 And when the day of Pentecost was fully come, they were all with one accord in one place.
Act 2:3 And there appeared unto them cloven tongues like as of fire, and it sat upon each of them.
Act 2:4 And they were all filled with the Holy Ghost,
There is no break in the sequence of referring to the 120.