It's set to 8 by default.
options... > settings: precision for direction selection (in º).
By default it's set to 45, which equals 8 directions.
90 = 4 directions
45 = 8 directions
30 = 12 directions
22.5 = 16 directions (decimal values are not possible though)
15 = 24 directions
11.25 = 32 directions (same issue as 16 directions)
Once you change that in the editor it will let you set those directions via the alignment compass.