What does Acts 20:15 mean?

Paul has faced several complications during his journey back to Jerusalem, but he is finally underway. He and his companions sailed from Assos to the city of Mitylene on the island of Lesbos. They continue skirting the province of Asia, in the southwest of modern-day Turkey, to Chios before they touch Samos on their way to Miletus.

If Paul had had his way, he would already be in Jerusalem. Personal conflict with both the church and the Jewish leaders in Corinth has thwarted his plans (2 Corinthians 1:15–16, 23–24; Acts 20:3). In exchange, however, he is able to spend time with the church in Troas (Acts 20:7–12) and the elders in Ephesus. Paul knows that something will happen in Jerusalem and the Romans will imprison him (Acts 20:22–23). It's not clear if he realizes the ordeal and travel will span five years and end up in Rome. By taking the many undesired detours, Paul can build up the churches and prepare them for his absence. They also encourage him so he can remember how his hard work has led to the salvation of so many in Galatia, Asia, Macedonia, and Greece.

Chios is an island south of Lesbos Island and directly west of modern-day Izmir, Turkey. Samos is an island southwest of Chios, between Ephesus and Miletus. Miletus is about 63 miles south of Ephesus. Accompanying Paul are Luke and an assortment of men from Turkey and Macedonia who are likely taking offerings from their home churches to Jerusalem (Acts 20:4; Romans 15:26). Among them is Trophimus who will be an unwitting catalyst in Paul's arrest (Acts 21:27–36).