There is a general formula for converting the Brinell indention to hardness,
Hardness Brinell = Load / (Pi /2 x D x (D - Sqrt(D^2 - d^2)))
where Load is Kilograms
D = Ball diameter in mm
d = impression diameter in mm
Thus for your test, 10 mm ball and 300 kg load and 3.9 mm...
