That's the number of players who were juniors or seniors that were drafted in the first round of the NBA draft in the last four years. The NBA wants to get their hands on those "immature, less developed" players because they think they will be better equipped to make them into NBA players. Since the pro game is different than college, it makes sense to want to get them early so they can mold them for that style of ball.

FWIW, Sr. never said "go to the NBA", he said "go pro". As a former D1 player, I'm sure he knows quite a few players that have done very well for themselves overseas. Our own Malcolm Delaney has been making around $2m/yr and even got a shot at the NBA after a few years in Europe. Not sure if that makes him Lavar Ball, who has made some bad decisions that hurt his kids, or Richard Williams, who got a lot of crap but helped his kids become elite.