nnml article number gaps

[nobrowser]

I just took a nnml group with 5000+ articles and split it in two.  I
hoped that the number of articles Gnus asks me about when I open the
group would be smaller.  It isn't, and I realize this is because it
simply takes the ordinals of the last and first article and takes the
difference, and no renumbering occurs when articles are deleted.  So
then I thought nnml-generate-nov-databases (or its wrapper command in
the server buffer) would do that.  It doesn't either.  Is there any
non-manual way of squeezing the gaps in article numbers after mass
deletion?