diff --git a/library/ecp_curves.c b/library/ecp_curves.c
index 7d312ca..f426e64 100644
--- a/library/ecp_curves.c
+++ b/library/ecp_curves.c
@@ -5150,6 +5150,8 @@
 
     RESET;
 
+    /* Use 2^224 * (2^32 - 1) + 2^192 + 2^96 - 1
+     * to modulo reduce the final carry. */
     ADD_LAST; NEXT;                                             // A0
     ;         NEXT;                                             // A1
     ;         NEXT;                                             // A2
@@ -5161,6 +5163,8 @@
 
     RESET;
 
+    /* Use 2^224 * (2^32 - 1) + 2^192 + 2^96 - 1
+     * to modulo reduce the carry generated by the previous reduction. */
     ADD_LAST; NEXT;                                             // A0
     ;         NEXT;                                             // A1
     ;         NEXT;                                             // A2