Relating to post http://forums.b2evolution.net/upgrade-from-6-8-8-fails-cannot-access

Where does the error page referring to the database version needing updating gets it's b2evo version from?

In the post firstmentioned @loobyloo3 gets the oddity that when updating from 6.8.8. to 6.9.7 the message reads Version 3.3.3 and

You have schema version «12365», but we would need «9960».
see http://loobynet.co.uk/ or
http://forums.b2evolution.net/media/users/loobyloo3/comments/p362230/database.woe.png?mtime=1527427979