The POP time is the time measured from the instant the ball hits the catchers mit until it hits the second baseman's mit.
2.0 is the magic time that most coaches are looking for. You do not have to have a cannon for an arm to get that but you need good technique. My son has a 70 mph arm, but has oftentimes gotten below 2.0 in practices and hits 2.1=2,2 during game situations.
It is a good idea to find a good catching coach that can instruct your son. They are much more difficult to find than hittting instructors. There is a great deal of technique to catching and throwing. Catchingcoach had a great description of the throw down on this web page about a month ago. You might be a ble to find it. Tell your son to work on his long toss also it will strengthen his arm.
"They tell us to take a round bat and hit a round ball and hit it square" Willie Stargell