To measure 20 kg using 8 to 11 weights of 1 kg, denote the number of 1 kg weights as $x$ (where $x$ can be 8, 9, 10, or 11). The remaining weight to achieve 20 kg will then be $20 - x$. The possible combinations of 2 kg, 5 kg, and 10 kg weights adjusted to match this remainder yield 8 different valid configurations.