I think I have the idea that a vassal army controls its own taxes, if 5% or more of his master's army. But numbers do not make sense in the demo. Shoni begins with six provinces, four of them controlled by the subjects, which can raise 750 men each. 4x750 = 3000. The leader of the clan had a heritage of two provinces, also begins with an entourage of 1,000 potential IIRC, which equates to another 2500.
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