Ordinarius, Index, or what else?

Meeting HERA project Sound Memory, Warsaw, 27-28 October 2016

In the middle of the Codex Nijmegen 402, which I have presented in Prague an intriguing small manuscript is bound: the Aenwijser om te vinden die Antiffens, written for the Round Beguinage of Amsterdam around 1600. What is the function of this little document? Is it a Liber Ordinarius in a nutshell, or is it a register?