Fuzziness parameter in a query

I'm trying to understand the documentation of the fuzziness parameter.

I'm not sure what the low and high values for AUTO mean.

Why is it that when I do a query with "AUTO:0,2" I get a result(supposedly an exact match), but when I do the exact same query with "AUTO:6,12" (supposedly up to two changes), I get no results...

What is your query and what do you expect to match and not match in the various cases? What is the mapping for the field?