This thread is about the character capacity of a CD-R disc Volume Label.
The reference you have made is to an ISO file naming convention. A file name and a volume label are not the same thing.
In any event, it isn't necessary to use "Max. of 31 chars (ISO Level 2)" to get long filenames in Windows. All you need to do is check "Joliet" and 64 characters will be available for Windows filenames.