That is the Chinese claim line.
Buffer zone is from Chinese claim line till Indian claim line (around 400m further inside from bend) plus some extra area for cushion on both sides so a total length of 2.8.
Any this line showed India penetrated deep inside Chinese claim line. In Feb China finally admitted India built tents at the bend.
Anyways now in Galwan there is no Chinese presence on Indian side of claim line and no Indian presence on Chinese side of claim line.
When is Modi going to name China? I've been waiting for one year, literally.