Fix semantically meaningful typos in comments

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/bignum.c b/library/bignum.c
index f1e5443..7981175 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1674,13 +1674,13 @@
         return( 0 );
     }
 
-    /* Calculate X*b as A + A*(b-1) to take advantage of mpi_mul_hlp */
+    /* Calculate A*b as A + A*(b-1) to take advantage of mpi_mul_hlp */
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     /* In general, A * b requires 1 limb more than b. If
      * A->p[n - 1] * b / b == A->p[n - 1], then A * b fits in the same
      * number of limbs as A and the call to grow() is not required since
-     * copy() will take care of the growth. However, experimentally,
-     * making the call to grow() conditional causes slightly fewer
+     * copy() will take care of the growth if needed. However, experimentally,
+     * making the call to grow() unconditional causes slightly fewer
      * calls to calloc() in ECP code, presumably because it reuses the
      * same mpi for a while and this way the mpi is more likely to directly
      * grow to its final size. */