The question, as stated, cannot be answered sensibly. A millilitre is a measure of volume, with dimensions [L3]. A gram is a measure of mass, with dimensions [M]. The two measure different things and...
gr is the abbreviation for the apothecary measurement grain
VIISS is 7 1/2 (the Roman Numeral for 7 is VII and Roman Numeral for 1/2 is SS)
There are 60mg (milligrams) is one grain,...