Probably best explained with an example, if you view http://musicbrainz.org/cdtoc/attach?id=KAlaiBbBW2C13N775QKOiDU.3U8-&tracks=17&toc=1+17+327405+150+17671+32863+56157+75202+99928+118183+152149+154677+172385+194389+217577+236998+255278+267566+281973+311642&tport=8000 whilst logged out of Musicbrainz, it says:

"We found discs matching the information you requested, listed below. If none of these are the release you are looking for, please see the instructions belowe."

Aside from the typo at the end, the main issue is that all that's shown is the discs that matched the TOC search. There are no instructions.