diff --git a/sc2/doc/devel/strtab b/sc2/doc/devel/strtab
index f111db4f6..74185ae5f 100644
--- a/sc2/doc/devel/strtab
+++ b/sc2/doc/devel/strtab
@@ -25,15 +25,25 @@ Followed by:
            4       offset from &StringCount until one char past the end
                    of the last string.
 
+For .ct files an item is as follows (new 256x24bit format):
+           1       Index of first clut in this item.
+           1       Index of last clut in this item.
+  For each item:
+    256 palette entries:
+           1       red value
+           1       green value
+           1       blue value
 
-For .ct files an item is as follows:
+For old .ct files an item is as follows (obsoleted by new 256x24bit format):
            1       Index of first clut in this item.
            1       Index of last clut in this item.
   For each item:
     32 palette entries:
            2       bits 0-4: blue value
                    bits 5-9: green value
-                   bits 10-15: red value
+                   bits 10-14: red value
+                   bit  15: specifies the interpolation mode for 3DO scaling
+                            (is ignored now)
 The full palette contains 256 values, which are the original 32 values
     multiplied by 1 to 8.