> Several list owners noticed this last night.

Noticed what?

> However these were  *not* the first digests.  What controls this?

It's not clear what your problem is, but subscription options controls who
gets them and the Digest= keyword controls the rest.

> I see there is a
> "digests.file" in listserv's home directory.  But this is a small
> file - perhaps only for those lists that have explicit digests in
> their headers.  The reported lists all have a digests= line.

Digest defaults to:    Digest= Yes,Same,Daily

This breaks down to:

Yes=  Create a Digest file.
Same= Create the Digest file in the same directory the Notebooks are
stored.
Daily= Send the digests out to those subscribers set to DIGEST at midnight
once each day.

These are all/other options:
Digest= Yes,where | Same,
[frequency][,when][,Size(maxsize)][,BOTTOM_BANNER]

I assume what ever problem you have lies here some place.