[DOC] (refract): add description of subroutine's goal

src/ts/refract/sub/refract_setscale.f

@@ -5,6 +5,9 @@ c 30/04/98 by Thomas Forbriger (IfG Stuttgart)
 c
 c set default scaling
 c
+c This subroutine sets the initial amplitude, clip and minimum offset
+c interval values.
+c
 c ----
 c refract is free software; you can redistribute it and/or modify
 c it under the terms of the GNU General Public License as published by