Note 2 at Ac 20:19: Paul, in a sense, was bragging on his own humility. That does not fit most people's teaching on humility, but it's our teaching that's wrong, not Paul's example. A person can be humble and know it. Consider that Moses wrote of himself as being the meekest man on the face of the whole earth (Nu 12:3).

Note 3 at Ac 20:19: There is only one recorded instance during Paul's three-year stay in Ephesus (Ac 20:31) where Paul was openly attacked (Ac 19:23-41), and that was by Demetrius the silversmith, not the Jews. Therefore, it is certain by Paul's statement here that there were many persecutions he endured that are not recorded in Scripture.