Just to make myself clearer, both Brix and SG are measures of density.
If you apply a "Brix correction factor" of 1,04, that means you divide the reading in Brix by 1,04.
Your refractometer tells you 12,0 °Brix, and you divide that by 1,04 and consider 11,538461, or 11,54.
Your refractomer...