From the Sunday Times:
It assesses shape, bounce, firmness and symmetry – all factors that add up to the bottom line.
S is the overall shape or droopiness of the bottom, C represents how spherical the buttocks are, B measures muscular wobble or bounce, while F records the firmness.
V is the hip to waist ratio, or symmetry of the bottom, and T measures the skin texture and presence of cellulite.
(via Boing Boing)