In this symbol, the diagram of a perimeter wall has the dot of emptiness placed at its centre. The dot of emptiness signifies that something is not known. Hence, the meaning of this Indus sign is unfamiliar or new walls.
Illustrative Text Reference:
Harappa: Pottery Body reworked: H-2548 A: Asko Parpola, B. M. Pande, and Petteri Koskikallio, 2010: Corpus of Indus Seals and Inscriptions: Volume 3,1: Page 351: New material, untraced objects, and collections outside India and Pakistan: Suomalainen Tiedeakatemia.
Comment:
You should note that the photograph of H-2548 in the Corpus is upside down. The inscription begins with a pictograph of the piece of pottery.
Image Credit:
New Walls: Lynn Fawcett, 2018.