The above replies are correct in that the 'positive' means definite, confirmed.
It's not actually the position of the static ports which creates the false descent at rotation. I believe the cause is position error.
Furthermore the same call is also used in the missed approach procedure where the aircraft must first arrest the descent and start to climb. The VSI may lag a little at this point thus the climb must be verified by at least two instruments. This also checks their servicability.
Back to thread topic......Pet peeve, comtrollers who always have to have the last word (very often female)!