sorry, I take that back.
Its actually the HARP core book with the Greater spider stats...
pg 156.
In M:AFG, table; 9.1 lists Large creatures as 20 attribute points.
But page 123 says monsters with magical abilities are one Monster level greater, so on Table 9.2 you use Class VI, which then meets the +36 stat point that the creature has.....
But even a Large creature, Class V has a stat of 100, giving it stat bonuses +10, making all skills and OB +10 greater than what they already are (as the Harp core uses 75 stats across the board).
Confused yet? I know I am...