It seems that the point buy system Mr 19 is supposed to be using has been quite horribly mangled. As such, I will try to explain it properly.

You start off with 10 in all stats. You have 18 points to distribute amongst them. Raising a stat costs 1 point per increment until 14 is reached (1:1 ratio). Raising a stat costs 2 points per increment from 15 and upwards (2:1 ratio). Lowering a stat from 10 gives a ½ point per decrement until 8 is reached (1:2 ratio). Lowering a stat from 8 gives a ¼ point per decrement (1:4 ratio).

To summarise:

All of your stats start at 10.

Reducing a stat to 4 from 10 gives **2** points.

Reducing a stat to 8 from 10 gives **1** point.

Raising a stat to 14 from 10 costs **4** points.

Raising a stat to 15 from 10 costs **6** points.

Raising a stat to 16 from 10 costs **8** points.

Raising a stat to 18 from 10 costs **12** points.