^^^ Agree w/ jlykos.
TS.com standard wisdom is "don't use rolloff, do it in post." If you use a cardiod mic, especially a small one that probably doesn't pick up much bass anyway, that is probably right. But if your recordings consistently have too much bass, IMHO it doesn't hurt to use a little roll off up front. You seem to have the sound pros battery box rolloff system. I'd say don't go much over 95 with the rolloff - "you can't put back in what you've taken out" - and even then, I'd only go that much if you use omnidirectional mics. When I ran SP mics I usually used 69 or none with cardiods. With omnis, 95 max. You can always do more bass rolloff in post; as jlykos points out, doing it up front will save time.
The numbers are the bass frequencies below which the bass will be rolled off. 888 is quite close to 1000Hz which is really midrange-- this is very "audible" bass. The farther down you go - 16 for example - you are talking about bass you can 'feel', which often comes across as the boominess that people find unpleasant in recordings, especially on weaker playback systems.
Metal shows probably have a lot of that.