This is a pictograph of a tally stick. The four horizontal notches on the stick mean that the unit count was precisely four.
Illustrative Text Reference:
Khirsara: Rectangular Seal: Krs-1 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 357: Collections in India: Suomalainen Tiedeakatemia.
Image Credit:
Indus Script Sign Number 2577: List of Sign Variants: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.