So am I. Besides that, here's what the SRD has to say about it
here:
Code:
Challenge Rating: Depends on Hit Dice, as follows:
Hit Dice Challenge Rating
1/2 1/6
1 1/3
2–3 1
4–5 2
6–7 3
8–9 4
10–11 5
12–14 6
15–17 7
18–20 8
Is your MM the 3.0 edition perhaps?