Help With PE!? Need Someone Who Is Good At The Theory Side of PE!?

In PE, we are doing a personal exercise programme (PEP) and I'm out of my target zone. My target zone is 143 beats per minute- 164 beats per minute. But its the 6th week of doing my PEP and my heart rate was 171 and recovery time was 3 minutes. Just wondering because I was out of my target zone, Is this bad? Because I know I wasn't working anaerobically.