Your numbers are slightly off. Specifically 8 and 9 are wrong and you haven't listed any of the alternates for 3-7. There are 4 basic shapes (plus zero) which consist of a straight line rotated 90 degrees. These make up 1-4. Then 5-10 are composites of these shapes (5 = 2 + 3 or 1 + 4 etc.). I've made a picture to more clearly demonstrate what I'm talking about

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The only rule about making the composite symbols is that the combined symbols can't have any overlap. They can only meet at right angles. That's why the symbol for nine can only be made of the primary four symbol and the primary five symbol. Using the secondary five symbol would have caused overlap. Etc. Etc.