This part of the documentation is not meant for end users of Coppermine, but only for developers. There is no support for this section, it comes as-is.
The updater (update.php) contains a hidden feature meant for development purposes: when adding the parameter debug to the URL in the address bar, the output will contain additional information - mostly the output generated by mySQL.
If you don't know what to do with this piece of information, then just don't use that option. The output generated (and particularly the error messages) don't mean that there is actually something wrong with the gallery. Instead, the output is meant for developing purposes. Non-developers should only use the hidden feature if a supporter explicitely tells them so on the support board and asks for the output or a screen shot.
Example usage: instead of going to http://example.com/your_coppermine_folder/update.php, go to http://example.com/your_coppermine_folder/update.php?debug to enable debug output on the updater screen.