New to Power: Calibration Help?

i’m new to power. my Quarq was just installed & i took it out for its maiden voyage today.
i did as i was told by my mechanic & before i started my ride i calibrated the Quarq using the head unit (an Edge 810 if that helps). The “Current Calibration” value showed “-256”.
but, being as i’m new to this i don’t know what the numbers from the calibration mean.

i was under the impression that it was supposed to be offset to “0”. is this not correct?
are calibration & zeroing different things?

any guidance would be greatly appreciated!

http://www.quarq.com/pages/getting-started/operation

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BOOM.
awesome. thanks.

for some reason every Quarq page i found in my Google results gave me a 404 error…whatever, thanks!