This is the noun time with the addition of some marks from a ruler. There is no straight edge, which implies that the ruler itself is missing. Therefore, this is a symbol for an approximate value. There are four marks giving three spaces, which translates as 'around three hours'.
Illustrative Text Reference:
Harappa: Seal: H-27 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 174: Collections in India: Suomalainen Tiedeakatemia.
Image Credit:
Indus Script Sign Number 2170: List of Sign Variants: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.