The technical explanation is that "8 pts head-light" means the balance point of the racquet as been moved 8 points, or 1" closer to the handle than normal. On an even balanced racquet (i.e. 0 pts headlight) that is 27" long, the balance point is at its midpoint, or 13.5". When a racquet is listed as head-light, it means that weight has been redistributed so that there's more weight in the bottom (handle end) of the racquet than the top (head end). To gauge how head-light or head-heavy a racquet is, we use points, where 1 point is 1/8". So a racquet listed as 8 pts head-light has had it's balance point shifted 1 inch toward the handle, which is would be 12.5". The same holds true for head-heavy racquets--8 points head-heavy would have a balance point shifted 1" toward the head, or 14.5" from the handle-end oft the racquet.
-Craig.