Why does equilibrium constant change when the reaction is multiplied by a number and nothing in the real has been changed?

As far as I know, a large equilibrium constant shows that the a reaction like the one below wants to complete:

$$\ce{B <=> A}$$

If A and B are gases, then K is: $$K_1=\frac{[A]}{[B]}$$

but when I multiply the reaction by 20 , K is $$K_{20}=\frac{[A]^{20}}{[B]^{20}}$$ while the same number of moles of B are consumed. If $\small K_1 = 10$ then $\small K_{20} = $$10^{20}$ so the reaction must be approximately complete. Why does this happen while the reaction materials didn't change?