The Knicks aren't done bringing players into training camp. From Shams Charania of Yahoo! Sports:
The Summers signing brings the Knicks to 19 total contracts. A team is allowed to bring a total of 20 contracted players into training camp, but must get down to 15 by the start of the regular season. Only 13 Knicks are currently guaranteed (not including Langston Galloway, who you'd imagine will comfortably make the roster after finishing Second-Team All-Rookie a season ago).
That leaves Summers, Travis Trice, Thanasis Antetokounmpo, Darion Atkins and Wesley Saunders all fighting for one final roster spot.