The section you mention lists the tags:
Adding Circuit Refs to AEDs
Each AED listed in The Circuit has a 32-character unique reference number in the form of a UUID: XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX. Robert Whittaker obtained permission from the British Heart Foundation to add these numbers to OSM. Please use the
ref:GB:the_circuit=*tag for this. Doing so confirms the matches in the Comparison Tool, and makes the comparison more reliable than just using proximity between the datasets. A semi-colon separated list of UUIDs can be added tonot:ref:GB:the_circuit=*to prevent incorrect matches in the tool.
The referenced “Comparison Tool” is this one linked further up the page.
You may also be interested in the slides linked to in this post.