Entries on Indexing

Hi, I am fairly new at indexing but I had a question and can't seem to find the answer.

When I am indexing it says that there can be one or multiple entries. Why do some files have one entry and others have 40 or another number? I am not sure what to put in all of those 40 entries when it is just one persons name.

Again, I am new at this so it may be a simple answer, but I would love to receive help on this.

Thanks!

If there are entries that don't have anything to put in them, you can mark them as blank. (ctrl+b while in the field)