The tables should be mostly self-explanatory, but maybe that's just my bias due to how closely I've worked with them. So here's a quick run-down:
- Use the first five entries to set the base hit dice, damage, armor, move rate, and number appearing, based on general size.
- If you add dangerous features or special attacks to the creature, add 1 hit point per feature (probably should limit this to +4 hit points.)
- Modify Hit Dice based on Body Size, Group Size, and enchanted, magical or demonic nature.
- Modify the number appearing by increments of 1d6 if the base number appearing is 3d6 or greater; modify by increments of +/-1 if the base number is 2d6 or less. Multiply by 10 for flocks, swarms, or tribes.
- Physical size also modifies base move, and magical, enchanted or demonic creatures have improved armor.