lining problem_medium and low LODs

Hello.


I am making a clothing. About my meshes..., but I'm confused about the following statement.

///
After using Decimate modifier, you need to fix lining issue. Top body mesh should be lined up with lower LODs bottom mesh. You can see the problem if you take a look from a view from front-bottom angle.

The meshes of your medium and/or lower LODs are not lining up correctly with the rest of the body. This can happen when you use a poly slider on your high LOD mesh to make the medium and low LODs instead of making use of the original medium and low LOD body parts. ///

Once again, I brought the original mesh body from EA and joined it to my polygon on blender.

And I changed the high LODs to medium and low LODs with a poly slider(Decimate).
I saved each one and uploaded.

Should I edit the original mesh (EA) on the lower LODs after decimating?
Or is it  mean my clothes line after decimating?


Sorry for my poor English.
Thanks,

mesh
drive.google.com/file/d/1XuEdUTNrxH7uZmNopHwHYd8XXP7h3ULK/view?usp=sharing