www.cnn.com/2015/01/22/us/nfl-patriots-deflategate-rules/
"According to NFL regulations, each team provides a dozen balls to the referee for testing
two hours and 15 minutes before kickoff. The
home team also supplies 12 backup balls, and
for outdoor games, the visiting team has the
option of bringing another 12 balls. In addition, the ball manufacturer -- in this
case, Wilson (cue "Cast Away" jokes) -- ships
eight more balls, in what the NFL scientifically
terms "a special box," directly to the referee.
The box is opened two hours and 15 minutes
before the game, and the referee marks each ball with a "K," to designate it for kicking."