Stereo Integrity TM65 MkII drivers...

DrNumbers

Your measured distances are the distance between the speaker and your ears. The distances you see in your Helix is the difference between: (1) your measured distance to the speaker and (2) the distance to the most distant speaker. For example, your RM is the furthest away at 53". Your left tweeter is the closest at 36". So the left tweeter gets delayed by the amount of time it would take sound to travel 17".

So it would appear that your DSP wants the relative difference in distance to your most distant speaker and not the actual distance. Ultimately, the distance and time measurements are designed to do the same thing.

Edit: I would double-check the manual just to make sure what the DSP wants for time alignment. My DSP uses the actual distance to each speaker to set delays.