The counter is instant, and so is Wix
Neither side of this pair waits on a timer.
Square reports a counter sale the moment the card is tapped and Wix reports a web order the moment it’s placed, so each side is corrected from the other within a few seconds. A Saturday queue at the till and a busy evening on the site can share one shelf without the counts separating.
The one slower path is stock you edit by hand: on the Wix side, edit it in the master store or QuickSync rather than on Wix itself, because Wix mirrors the master’s catalogue and direct edits are overwritten on the next sync.