Here the word "they" probably refers to the Gentiles at the court. They reacted against the Jews who had brought Paul before the judgment seat. (See: [Acts 18:12](./12.md))
"Gallio dismissed them from the judgment seat." Here "judgment seat" refers to the place where Gallio sits to make legal decisions in court. AT: "Gallio made them leave his presence in the court" or "Gallio made them leave the court" (See: [[rc://en/ta/man/translate/figs-metonymy]])