The box marked miscellaneous may contain the detail a family will someday search for.

Sorting is done by present usefulness, and the future has different priorities. What goes into the miscellaneous box is whatever had no obvious category: the loose photographs, the note with no date, the ticket stub, the thing nobody could place. Those are exactly the items a grandchild will want, because the categorised things are the ones that were already understood. Value in this area is impossible to judge from where you are standing.

So be slow about clearing out the unclassifiable, and slower still on someone else’s behalf. If you must reduce it, keep the paper with handwriting on it, since that is the part nobody can reconstruct later.