"The general rule" (1" of fish per gallon) is only that. General.
If I thought the way as the "general" public, I'd have a "general" aquarium. You raise a good question, so, please allow me discuss this with you, as I'm feeling, uh,
inspired.
When many ppl begin their fishkeeping days, most are inspired by a beautiful aquarium they saw, or maybe they just like fish. No matter, you like fish, you want to have some, what can I do?
Like any other hobby, you have to have a plan. When you look at that 10g, what do you envision? What do you
wish it would be/look like? Write all of that down so you don't forget, or you can add to it later.
If you really like fish, you would care for them as you would a loved one (person), just like a dog lover would do for their dog. You treat them as part of the family. Ok, maybe you don't, whatever, you HAVE to consider the fish. If you're going to keep a living being, you need to supply it with its' needs, or else it will die sooner or later.
Getting closer to the point, you have to mentally envision fish in your aquarium, say when you're at the fish store with wallet in hand. You have to know what you want before you can get there. Four mollies isn't a lot for a 10G, but if you're breeding them, it is more than plenty. Generally speaking, the more calm the aquarium, the more calming the effects have upon the viewer. Some people have issues with being calm, and they prefer having a busier tank to reflect their busy lifestyle.
The point: Fishkeeping is NOT Calculus. It's not how many fish you can theoretically cram into a tank, but rather something you do for yourself with a loving nature.
This enables you to be successful, not a
general rule.
When you envision your tank, you will see something. Maybe it's lots of little fish. Maybe it's not, but rather 2 bigger fish. Maybe a mix. When you decide what you want, ask yourself, are cramming 30 neons in a ten gallon good for them? Would you like being crammed with 30 ppl in a small room? It's all relevant, and you can discover this with observation, which you already have, or else you wouldn't be asking the question in the first place.
To further complicate things, you have to worry about how big the fish will get, if they will reproduce, their temperment, the physical body relevant to the type of tank, blah blah blah...the list goes on and on. General rules were made for the inexperienced (you gotta start somewhere
). Common sense is better.