diff --git a/settingtypes.txt b/settingtypes.txt
index a5697d8..bd16a40 100644
--- a/settingtypes.txt
+++ b/settingtypes.txt
@@ -28,7 +28,8 @@ snow_min_height (Minumum Height for Snow Biomes) int 3
 #Disable this to stop snow from being smoothed.
 snow_smooth_snow (Multiple Snow Levels) bool true
 
-#mapgen rarity in %.
+#mapgen rarity in %. Note that this and mapgen_size do not work right because
+#sinus instead of Gauss curve is used as estimation.
 snow_mapgen_rarity (Snow Biome Rarity %) float 18
 
 #size of the generated… (has an effect to the rarity, too)