Hi Geoff0409
I've read of others getting a FG reading of 0.900, although I've never achieved that myself.
According to this online calculator
https://chasethecraft.com/calculators/#sugarwash adding 6kg sugar to make a total volume of 27 litres would result in a specific gravity of 1.0893, which would equate to 13.7% ABV, give or take.
You could always confirm the calibration of your hydrometer in distilled water, just to be sure.
Or could also make a very small sugar wash with known SG from the calculator above to confirm your new hydrometer?
good luck
BK