populations of realm types

The guidelines for populations by realm type do not seem to be continuous. For example, the number of families given for a barony is 120-200, while the next step up (march) has a suggested population of 960-1280 (the same thing is true for realm size: e.g., a march is 3-4 hexes while a county is 15-30 hexes).
How would you suggest handling realms of an intermediate size? My inclination is to “round up” and thus consider a realm with, for example, 500 families to be a march rather than a barony, but I’m not exactly sure how this will interact with the other moving parts within the system (like the market characteristics).
The other alternative would be to not allow (I am only talking about the setting creation process here) intermediate size realms. For example, there would have to be five contiguous baronies before a march could arise.

Untimely, the ranges are merely guidelines to help you, so don’t let them straightjacket you. The campaign world is a big place and all sorts of realms are possible. You can absolutely have “big baronies” or “small marches” or anything else.

That’s more or less what I was assuming, I just wanted to make sure there wasn’t a “best practice” suggested that I was missing. Thanks for the clarification.