The DMA 35N was the second handheld density meter launched by Anton Paar in the 90's. It is a bit old and likely needs a calibration adjustment. You can do this using distilled water. Do you need a user manual?
The finished vodka may contain some flavors or sweetener. The density of these materials act like water and show up as a dilution of the sample causing them to read below the label claim. The heart cut from your still should be just ethanol and water which should agree between the hydrometer and DMA 35N. Results on the DMA 35N, as with all DMA 35's after this model, can display results of %ABV at 20 C or Proof at 60 F. When comparing the results, make sure the temperature conversions are correctly compared. The DMA 35 series use a factor called the "Temperature Coefficient" to convert the density of the sample at ambient temperatures to the correct result at 20 C or 60 F. The Temperature Coefficient for calculation is likely to have changed. The user manual shows the steps for changing this Temperature Coefficient within the meter.
Start with the distilled water check procedure. If the water check is accurate, then the Temperature Coefficient can be adjusted to provide better results that are closer to your hydrometer.
