Take all fielding metrics with a grain of salt. Most do not take into account the type of pitchers the fielder plays behind, and since most range based stats are based on chances and chances compared to the rest of the league, so for example an OF that plays on a team full of groundball pitchers has a disadvantage.
Fielding stats, even advanced ones that sabermetric guys swear are useful, should really just be looked at as a guide. They won't tell you a really bad fielder is good, or a really good fielder is bad, but be careful comparing similar players using these.