The post you linked quoted & linked an NBC article, but cut off the critical
last paragraph in the article it was quoting:
"NBC Sports reported Wednesday that according to an NFL source, a review has determined the Patriots' balls were properly checked by the officials before the game, meaning the pressure was between 12.5 PSI and no more than 13.5 PSI. When the balls were tested at halftime, 11 of the 12 balls were two pounds below the mandatory minimum, NBC Sports reported."