Calculating the sensitivity of an ADC with respect to resolution
2/20000 = 1/10000 = 100 micro-ohm, as you say.

The "problem" is almost certainly with the type setting. 

They have used "m" for micro. This may have started off as Greek "mu" which can be transliterated as u as in uF. 

BUT I have seen a text where "mF" was displayed BUT when you pasted the text and changed the font it changed to a Greek "mu".