Note 9 at Acts 18:10: Paul already had a good idea of how many Christians there were in Corinth. He was the one who had introduced the gospel of Jesus to them. Therefore, this must be speaking of others who were not yet Christians but yet were God's people.

God in His foreknowledge (see note 4 at Jn. 13:5, p. 475) knew those who would accept the gospel if given the opportunity and He must have been the group He was referring to. He urged Paul to stay and continue to preach the good news till all those who were ordained to eternal life believed (Acts 13:48).