Use of 'thereof'

[Offroad]

Dear teachers

Am I correct with the following interpretation?

The prisioners from corridor A helped her escape before the release thereof was officially signed.

'thereof' means 'of them' and refers to 'prisioners'.

Many thanks

[Route21]

As an NES but not a teacher, the word "thereof" sounds a tad inappropriate to me.

Regards
R21

[Rover_KE]

The word thereof is mostly used in legal documents or other very formal writing.

Use 'their release' instead of 'the release thererof'.

Note the spelling of prisoners.

Rover

[Offroad]

Yes, most dictionaries state 'thereof' is rather formal. In fact, I was just checking if I had understood how to use it as I am writing a formal document.

Thank you