It looks like this:
9 - 1
10 - 2
11 - 3
12 - 4
13 - 5
14 - 6
15 - 8
16 - 10
17 - 13
18 - 16
The first column is the ability score. The second column is the cost in points to purchase the ability score. Every ability score starts at 8, for free. From there, you have 25 points to spend.
Also, if you're playing a race other than human, your race's ability score increases and decreases aren't added or subtracted until after you spend all of your points.
Hooray!