A3 11-3/4" x 16-1/2" 297 x 420 mm
A4 8-1/4" x 11-3/4" 210 x 297 mm
8x10 8" x 10" 203 x 254 mm
dot pixels calculation
W=format.w/pen_size
H=format.h/pen_size
so
W= 203/0.3 = 676
H= 254/0.3 = 846