Then they (a)returned to Jerusalem from the mount called Olivet, which is near Jerusalem, a (b)Sabbath day's journey away.
Returning from the ascension
v.12 (a) the disciples, probably more than just the twelve, were in Bethany, on the Mount of Olives, where He ascended into heaven, Lk 24:50. Before that, Jesus had met them in Galilee. Many people confuse the great commission in Galilee as His ascension, but it is clear that the ascension took place in Bethany, Lk 24:50, and the great commission was in Galilee, Matt 28:16-18.
v.12 (b) a Sabbath’s day journey was 2,000 cubits, about 3,000 ft., according to Num 35:5. The Mount of Olives was within this travel limit, Acts 1:12, but Luke 24:50 states that He led them to Bethany and was ascended into heaven; according to John 11:18, Bethany was about 9,000 ft. from Jerusalem. So we have a discrepancy of 6,000 ft. Any time you come across something that seems like a contradiction in the Bible, use it as a chance to dig deeper because the Word of God does not contradict itself.
John 11:18 is focusing on Jesus raising Lazarus from the dead. Mary, Martha and Lazarus lived in Bethany and this was a common place for Jesus to stay when He was in Jerusalem. The town of Bethany was not big, but was at least bigger than 2 miles. I believe that Mary and Martha’s house was in Bethany, two miles from Jerusalem, while the Mount of Olives and the place of the ascension and Bethpage, were within a Sabbaths day journey from Jerusalem, but still within the borders of the town of Bethany. So when the Bible states that Bethany is two miles from Jerusalem, Jn 1:18, and also states that the disciples were a Sabbaths day journey away from Jerusalem, but still in Bethany, these statements agree because the town of Bethany was bigger than two miles.