Font size in pixels (width × height). Not every VT version supports all sizes.
0 = 6×8
1 = 8×8
2 = 8×12
3 = 12×16
4 = 16×16
5 = 16×24
6 = 24×32
7 = 32×32
VT version 4 and later additionally:
8 = 32×48
9 = 48×64
10 = 64×64
11 = 64×96
12 = 96×128
13 = 128×128
14 = 128×192