Base Run HR vs Pace Difference

Should there be a difference when you change your base runs from pace to HR?

My suggested pace right now is 5:30 min/km and for HR it suggests 142bpm.

My last 3 runs (base) were all around 7km, pace around 5:40 min/km and average HR around 138-140bpm (average HR to sustain that pace at the end was 148 because first 2km heart rate is still very low)

Now I'm wondering what the 142bpm suggestion is about, should I focus on training around that heart rate or is it about the average for the full run? At 142bpm I would definitely not be able to run 5:30.