Why would you need to include those hours? Are they so many that they make your overall number improve? Or do you have too little hours, and are looking for a quick boost? If you have enough time, don't include it. If you don't, then put in some more time.
Yeah, but do enough volunteering to where those hours are small part of it (it takes resources to train you, and if that's the majority of your volunteering, then one might wonder whether you contributed much).