The Indus Dictionary Project
In this section, the little roof shape that you can see on the left is used to represent the sky.
For image credits, please see below.
Indus Script Sign with a Number: Sign List of the Indus Script: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.
Indus Script Signs without Numbers: Lynn Fawcett, 2017 - 2019.