That was just showing you that to start off with you have your R, G & B values as seperate memory, and only the lower bits are actually used.

When you''re converting from 24bit, each value has 8 bits - 1 byte.
So those should have actually been:
000 RRRRR
000 GGGGG
000 BBBBB

Because we have already mod''d with 32, the upper 3 bits are gone.