ash: better comment. no code changes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/shell/ash.c b/shell/ash.c
index bb9464a..35d5cde 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -6400,7 +6400,7 @@
 	case '7':
 	case '8':
 	case '9':
-		num = atoi(name); /* number(name) fails on ${var#str} etc */
+		num = atoi(name); /* number(name) fails on ${N#str} etc */
 		if (num < 0 || num > shellparam.nparam)
 			return -1;
 		p = num ? shellparam.p[num - 1] : arg0;