9.5 Brix is 1.037 in an aqueous (water-based) solution. During and post fermentation, you now have a mixture of ethanol in solution, throwing the calibration of your refractometer off.
You need to take your starting Brix reading and throw it into a conversion tool such as this spreadsheet
. Or, you can use this correction formula:
Here is the correction formula:
SG = 1.001843 - 0.002318474*OB - 0.000007775*OB*OB - 0.000000034*OB*OB*OB + 0.00574*FB + 0.00003344*FB*FB + 0.000000086*FB*FB*FB
SG = actual specific gravity
OB = original Brix
FB = final Brix
Alternatively, you could also take a hydrometer reading to double check.