diff --git a/func/Module_precisely_align.py b/func/Module_precisely_align.py
index 009c642..651cff8 100644
--- a/func/Module_precisely_align.py
+++ b/func/Module_precisely_align.py
@@ -1547,6 +1547,7 @@ class Data:
                 self.BCG_early = False
             elif self.approximately_align_pos < 0:
                 self.BCG_early = True
+                self.approximately_align_pos = - self.approximately_align_pos
             else:
                 self.approximately_align_pos = 0
                 self.BCG_early = None