« Reply #8 on: Sunday 03 April 16 10:54 BST (UK) »
it's a numbered correction to the certificate.
Not to the certificate, but to the original registration, made at the time of entering. Corrections made later are handled differently.
Just noticed that on a copy of one I have, albeit it was a scan from a relative and she's left off the annotation on the extreme left of the certificate. There are numbers in two of the columns.
I've a local Register Office hand written copy of a death certificate where the surname was originally entered incorrectly, but was changed a few days after registration. That includes a statement to the right with the full details of the change.
(KENT) Lingwell, Rayment (BUCKS) Read, Hutchins (SRY) Costin, Westbrook (DOR) Gibbs, Goreing (DUR) Green (ESX) Rudland, Malden, Rouse, Boosey (FIFE) Foulis, Russell (NFK) Johnson, Farthing, Purdy, Barsham (GLOS) Collett, Morris, Freebury, May, Kirkman (HERTS) Winchester, Linford (NORTHANTS) Bird, Brimley, Chater, Wilford, Read, Chapman, Jeys, Marston, Lumley (WILTS) Arden, Whatley, Batson, Gleed, Greenhill (SOM) Coombs, Watkins (RUT) Stafford (BERKS) Sansom, Angel, Young, Stratton, Weeks, Day