Don't use it. It's bad.
The idea was kinda ok but it just didn't work too well. The idea was to build a sort of singleband compressor behavior into the multiband compressor; basically we check if the total level is too high which bands contribute the most to that, and lower those.
It's there for compatibility with old preset (actually that's the case for both "Classic" compressors).
And indeed, version 7.60 is available, it has more features, sounds better and uses about 20-30% less CPU power... so...
