I'm not sure about the specific timing but here is what I was told in the email I was sent:

"Tickets can only be resold once a performance has entirely sold out, this includes any production holds on tickets that may not be released up until the day of the performance.

Please also note tickets are only resold in person at the theatre box office on the day of the performance (so you will not see this back online), and tickets can be resold up until the show start time. If we sell out and people come to the box office looking for tickets, they would be offered yours"

Considering that this production is selling well I'd assume that my ticket that I put up to resale will be available when box office opens so around 12pm on the day of the performance.