I've looked a bit at military history and it is interesting to see how consistent they generally are. They'll have a squad of about 10, though the variance can be up to 50%, grouped into companies of ~100, grouped into legions of ~1000, into armies of ~10,000. It wasn't until the 20th Century that armies could become really huge. But the most all-purpose and independent units tended to be in the 100-150 range. Big enough to have enough people to do everything you typically need to do with adequate redundancy. Dunbar's numbers are good enough rules-of-thumb. Some people have better social memories and so will have larger Dunbar number capabilities, just as others have smaller.