Fix subpartitionof flag
diff --git a/partition.cpp b/partition.cpp
index c532fa8..e419579 100644
--- a/partition.cpp
+++ b/partition.cpp
@@ -349,7 +349,7 @@
 			Wipe_Available_in_GUI = true;
 			Wipe_During_Factory_Reset = true;
 		} else if (strlen(ptr) > 15 && strncmp(ptr, "subpartitionof=", 15) == 0) {
-			ptr += 13;
+			ptr += 15;
 			Is_SubPartition = true;
 			SubPartition_Of = ptr;
 		} else if (strcmp(ptr, "ignoreblkid") == 0) {