Did you convert the Brix reading of 6 for a final gravity? Refractometers can't be used once fermentation has begun without some calculations to account for the alcohol. A 6 is a very high FG, so I would hope you haven't bottled until you take a hydrometer reading!
Anyway, the easiest way to figure ABV is to convert your brix readings to SG and then do some simple math. (OG-FG) x 131= ABV.
So, in this case, if 6 is really the FG (and I hope that's wrong!), you have:
(1.048-1.024) x 131= 3.1% ABV
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