They have up to 7 days to return them if not sold:
“14.06 Visiting clubs which have requested an allocation of tickets for the whole or part of the segregated area may return any unused tickets to the home club
without payment up to seven days prior to the match, unless otherwise agreed by the two clubs in writing. After this deadline the visiting club must pay for the
whole allocation, irrespective of whether all the tickets have been sold.”
So that means by Thursday, unless a separate arrangement has been made.
I suppose though the latter is possible here, as it looks like we have been given the area behind the goal, (similarly to our North Stand) maybe it would make no difference to Waregem if we don’t sell them. Their supporters (who remember have to travel for this match too) probably won’t take up the excess.