You know what Tati - this has similarities to that other BMD thingy where the GRO corrected the 'wrong' birth entry .... or similar logic which turned out to be how they could best manipulate the Indices in later years to correct a 'problem'....
So as it seems Pressdee-Wotsit is also 6d 551 ..... it breaks the '2 couples per page' rule, so an anomoly is trying to be corrected !
The best way to find out whats going on is to approach the relevant Birmingham Registry Office and get them to cross-check their files ...
An individual can ONLY have ONE entry - if they were previously married that info is on the register ENTRY itself, eg WIDOW etc - not the Index .... [also thats what you see on Birth Certs 'previously Bloggs, formerly Smith ...' etc]
Hopefully someone with in depth knowledge of the processes involved can comment ?