MMEL is master document.
An MEL can be more restrictive by adding additional limitations.
It can never be more lenient.
In reference to MMEL rev 60 (outdated), it refers to CDU/MCDU repair category C and 1 required for dispatch.
It means that with one CDU inoperative, only 1 pilot can enter information.
Some companies require a dual installation for RNP1 PRNAV RNP Approach types, thus requiring both CDU/MCDU to be operational