Additional State Pension

My ex-husband has sent me [in anger] an annual report prepared by his deferred final salary pension scheme.
It shows the effect of sharing on his pension after my share was transferred out.
Their report includes a DWP Basic and Additional State Pension forecast based on his NI contributions to date.
The report shows an Additional State Pension forecast, based on his current NI contribution record, of almost £3,000 a year.
As far as I'm aware the pensions he's contributed to have always been contracted out.There was no declaration of a SERPS pension in form E.
A footnote says "The amount of Additional State Pension shown may change if you have been a member of a contracted-out pension scheme"

Does that mean that this Additional State Pension may not in fact exist?

OK -
UKGov website says:
"While you are contracted out, you will not normally build up additional State Pension, but you are compensated for this. The way you are compensated depends on the type of scheme you are in:
* if you are in a company or occupational pension scheme, both you and your employer pay a reduced rate of National Insurance contributions"

So this additional state pension probably came from early pensions that weren't contracted out, which we probably cashed in in the early days.
I expect the SERPS contributions could not be cashed in?
I read somewhere: for pensions on divorce get the employment history - cashing in like you used to be able to doesn't mean there's no pension left to share - always look for SERPS.