Insertion Resistance of Current Transformers
As JohnD hinted, the impedance ratio of a transformer is equal to the square of the turns ratio.

So if you have a 1000:1 transformer with a burden resistance of 100 ohms, the "reflected" resistance on the primary will be

$$\frac{100 \Omega}{1000^2} = 0.1 m\Omega$$

If you change the turns ratio to 1000:10 (= 100:1), but keep the burden resistance the same, the reflected impedance becomes:

$$\frac{100 \Omega}{100^2} = 10 m\Omega$$

... which is 100&times; as large, not 10&times;.