A silkworm spins its cocoon in a figure of eight pattern. Hence, it may be that this symbol is a pictograph of a cocoon. The symbol is related to archaic versions of the Chinese character yāo 么. The modern Chinese character is the adjective tiny, small, or fine. In Indus script, Mahadevan's sign number 410 is the adjective fine.
Illustrative Text Reference:
Harappa: Tablet in bas-relief: H-1994 A: Asko Parpola, B. M. Pande, and Petteri Koskikallio, 2010: Corpus of Indus Seals and Inscriptions: Volume 3,1: Page 273: New material, untraced objects, and collections outside India and Pakistan: Suomalainen Tiedeakatemia.
Image Credit:
Indus Script Sign Number 410: Sign List of the Indus Script: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.