You get 16 points to buy your ability scores using the chart below. The result is exactly like the standard 28-point buy, it's just faster.
| Ability | Cost |
|---|---|
| 18 | 14 |
| 17 | 11 |
| 16 | 8 |
| 15 | 6 |
| 14 | 4 |
| 13 | 3 |
| 12 | 2 |
| 11 | 1 |
| 10 | 0 |
| 9 | -1 |
| 8 | -2 |
Why...
Why not make 10 the zero point of point buy? Then 11 is 1 point, 12 is 2 points... easy right? Very quick to remember. And since every stat is 2 points cheaper, you can reduce the total amount by 6x2 = 12 points, from 28 to 16.
I've spelled it out above. You generate exactly the same stats as with the 28 point buy, it's just faster.
This has been bugging me ever since 3E came out...