§ 598 Disposition of ballot - When juror is absent or excused.

Here's a plain English summary of this rule:

When picking a jury, each juror's name is written on a ballot and drawn from a box. If a person is absent when their name gets drawn, or if they get excused from serving, their ballot doesn't just disappear. Instead, the court folds it back up and puts it back in the box.

This happens right after the jury is sworn in. The point is to keep the process organized so the court knows which names have already been used and which ones are still available if more jurors are needed later.