Gail - many thanks. The entry was explained to the solicitor at the time in our letter dated 8th May and if they are still acting for you then it might be worth speaking to them and asking them to respond to same as directed in their letter
The alternative is that you can apply yourself for removal of the entry using form CN1 -
Notice: cancellation (CN1) - GOV.UK
The form should be accompanied by a stat dec/statement of truth by yourself stating the facts with regards what happened and why no inheritance tax was payable.
The solicitor can, if they are willing, provide a certificate to that effect hence my suggestion of checking with them first
CYM891493