Remember, this isn't a performance plan. It's a fitness plan. Keep the intensity LOW here. Between 60-70% of your max heart rate. That's why there's 30 seconds rest. Have a drink, wiggle your backside, let you heart rate settle if it was spiking. If you're focussing on rowing in Zone 2 (60-70% hr) but also rowing this at 2K+18 pace, make sure your HR doesn't break out of 70%. HR takes priority. Slow down if you go over 70%. If you're sticking to 2K pacing, stick to 2K+18.