For us, they didn't give much rest for the first two. You paired up for push-ups/sit-ups and you would alternate, so you do push-ups, then rest while the other guy is going. And you'd keep count out loud of how many push-ups/sit-ups the other guy was doing. The big problem with that is sit-ups came first, so if you did sit-ups first, you'd then have to hold the other guy's feet when it was his turn, which can wear out your arms if you're doing it right. Then you'd have to go right into push-ups.
The last PRT was much more by-the-book in terms of allowing sufficient rest, because it's the only PRT conducted at OCS that actually goes in your record as the PRT for that cycle. So you won't need another one for about six months.