What do these mysterious numbers in the subject line of arXiv mailing list emails mean?
Straight from the horse's mouth: there is no fix, but an update is on the list of things that "will be done when they're done".


  You may safely ignore the numbers after the text "class mailing" as
  they are used for internal audit code and essentially meaningless from
  a user perspective.
  
  We do have plans to update the mailing code at some stage, but the
  time-line is unclear due to limited developer time.