I suggest you just stick with the analog scale you read off the refractometer. Digital readings only add the illusion of accuracy.
The measurements are only as good as the calibration and the quality of the representatively chosen sample to measure. Honestly, of what use is a reading that is accurate to +-2% rather than only 5%? You won't respond differently.
Although I like my lab toys, I use a simple analog refractometer to monitor my vineyard. I choose to harvest based on taste and practical factors like tank space, weather and labor availability. Whether my brix are 21.0 or 21.5 doesn't matter to me. Acid does matter though. Brix comes in 50lb bags, if needed.