This is a pictograph of a pack with a wheel inside it. It is an ideograph for a pack that is transported by wheels. Hence, it is the noun cart load.
Illustrative Text Reference:
Mohenjo-daro: Seal: M-1721 a: Asko Parpola, B. M. Pande, and Petteri Koskikallio, 2010: Corpus of Indus Seals and Inscriptions: Volume 3,1: Page 29: New material, untraced objects, and collections outside India and Pakistan: Suomalainen Tiedeakatemia.
Image Credit:
Indus Script Sign Number 1010: List of Sign Variants: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.