There is only a few words about the VG_A_8 format in the 1.1 spec:
The VG_A_8 format is treated as though it were VG_lRGBA_8888, with
R=G=B=1. Color information is discarded when placing an RGBA value into a
VG_A_8 pixel.
So what does the 1 in
Code :
R=G=B=1
mean?

Is it stand for 255 (0xFF) or 1 when the value for R/G/B is [0..255]?
(I think 255 is reasonable but 1 is not.)