Munin answered your question pretty straightforwardly.
But in either case you can probably assume the level of familial ties between members of the hardhold's gang and the holding is quite strong. If even half the gang have wives or husbands, children, brothers or sisters. You can find that a gang size of 50 can have a direct influence of potentially 200 of the people in the settlement. Assuming that the gang came from the settlment and didnt just happen to roll in one day. These are probably question you'll want to ask your hardholder too, because both can have some neat implications. If the ties are strong, are there family based competition in the hardhold? Does that create tension in the ranks of the gang? Do some people use their authority in the gang for personal gain? If the gang rolled in one day, who were the big losers of that movement, are they or their familial ties bitter about the whole thing? Just fun little toys you can play with.
If its of any particular interest, the actual population number doesn't really matter at all. It simply determines the scale of the settlement. If the base was 2,000 to 3,000; small was 750-150; and large was 5,000 to 6,000.... everything can function without changing anything. The barter scales naturally behind the scenes without the mechanical numbers needing to differ.
Likewise, in extremely low or extremely high variants, you can modify the scale of people per gang size in the same way. So you could say a small gang (3-10 people) is instead (5-30). This values do assume a certain heroic level of combat potential from the player characters (a gun lugger beating up 3 becomes about the same as a gun lugger beating up 25.) But still, it is entirely without the mechanics of the game to handle it. Further more, if you run into any problems, either with internal logic of the mechanics you want, the danger level, or an imbalance between the assume social connections of your game. Just ask, we've lots of home rules and solutions to various things we'd be willing to share.