Those are just three pre-defined symbolic names for particular percentages, but programmers can specify any desired percentage for the carveout, as noted in the first part of the relevant sentence (my bolding):
The API can specify the carveout either as an integer percentage of the maximum supported shared memory capacity of 164 KB for devices of compute capability 8.0 and 8.7 and 100 KB for devices of compute capabilities 8.6 and 8.9 respectively, or as one of the following values:
{cudaSharedmemCarveoutDefault,cudaSharedmemCarveoutMaxL1, orcudaSharedmemCarveoutMaxShared.