diff --git a/include/sys/sa_impl.h b/include/sys/sa_impl.h
index 744c8dcb7dfb..46a7cbf8080e 100644
--- a/include/sys/sa_impl.h
+++ b/include/sys/sa_impl.h
@@ -167,8 +167,8 @@ typedef struct sa_hdr_phys {
 	 * | hdrsz  |layout |
 	 * +--------+-------+
 	 *
-	 * Bits 0-10 are the layout number
-	 * Bits 11-16 are the size of the header.
+	 * Bits 0-9 (10 bits) are the layout number (0-1023)
+	 * Bits 10-15 (6 bits) are the size of the header (0-63)
 	 * The hdrsize is the number * 8
 	 *
 	 * For example.