The adjudicator found as fact that the suspension was posted before the appellant parked.
There was a case some time ago where (IIRC) a motorcycle or scooter was parked before a suspension notice was posted. (IIRC again) The adjudicator held that the notice being posted after the vehicle had been parked did not invalidate the contravention, but then went on to uphold the appeal on some ground that I struggled to follow.