In this Indus symbol, a marker stone is superimposed on a track. Therefore, it refers to the land or terrain surrounding the track.
Illustrative Text Reference:
Mohenjo-daro: Seal: M-1820 a: Asko Parpola, B. M. Pande, and Petteri Koskikallio, 2010: Corpus of Indus Seals and Inscriptions: Volume 3,1: Page 56: New material, untraced objects, and
collections outside India and Pakistan: Suomalainen Tiedeakatemia.
This is Mahadevan's sign number 253, which I have redrawn to better reflect the original.