I don't know whether they just need to find a few more to make up the number, or if they need to start from scratch tomorrow. I do know that a new pool of jurors turn up on Monday each week and there is an excess over what is needed so the ones not selected for a trial beginning on the Monday have to return each day until they are picked.
So they have a better chance on a Monday,rather than a Thursday when the pool of jurors had been diminished.