I don't believe you will be able to determine the %ABV from that refractometer, at least not as easily as I suspect you are thinking it will be. If you are a winemaker you can measure the sugar content of the juice from the grapes, usually in units of Brix. From that one can infer a potential alcohol content of the finished wine. It is also possible to do a calculation to determine the alcohol content by using measurements of the juice and wine. This is because the sugar content drops in concert with an increase in ethanol. But if you just measure a random wine with a refractometer there's no way to know what the value means. Wine is not a simple ethanol-water mixture.