Since GPS will not work indoors the PACE part of the Pa:Hr will not be accurate. Hence the specific instruction to NOT adjust speed or gradient once you start the test. This way you know the the pace stays constant and all you nee to look at is how much the HR drifts upward. I typically analyze it this way.
Using your cursor select the first half of the post warm up test by clicking and dragging the cursor over that section. You will see the average HR for the first half of the test displayed to the right (may need to scroll down). The repeat this process for the second half of the test. Divide the second half average HR by the first half average HR to see the % drift. For example: 1st 1/2 avg HR= 148. 2nd 1/2 avg HR=156. 156/148= 1.054. Or a drift of 5.4%.
If you did this or something similar and got 1% then you were well within your aerobic threshold at your initial HR.