Three rods: three. And here the counting pictures stop — four horizontal strokes became too easy to misread, so from four onward the numbers got real characters of their own. Three is also where "many" begins: three trees are a forest, three people are a crowd. You have seen this trick before.
A piece of culture
Among three walkers, my teacher Confucius said: 三人行，必有我师 — "when three people walk together, one of them can be my teacher." You can already read the first two characters. It is one of the most quoted lines in Chinese, a whole philosophy of learning in seven characters: everyone you meet knows something you don't. Keep the good, correct the bad you recognize in yourself — 2,500 years old and still the best study advice there is.