doc
diff --git a/skeletons/per_decoder.h b/skeletons/per_decoder.h
index 24dfe93..710f4ee 100644
--- a/skeletons/per_decoder.h
+++ b/skeletons/per_decoder.h
@@ -35,7 +35,7 @@
const struct asn_TYPE_descriptor_s *type_descriptor, /* Type to decode */
void **struct_ptr, /* Pointer to a target structure's pointer */
const void *buffer, /* Data to be decoded */
- size_t size, /* Size of data buffer */
+ size_t size, /* Size of the input data buffer, in bytes */
int skip_bits, /* Number of unused leading bits, 0..7 */
int unused_bits /* Number of unused tailing bits, 0..7 */
);