This is a pictograph of a slope. It has a steep gradient. Hence, Mahadevan's sign number 1385 means steep slope.
Illustrative Text Reference:
Kalibangan: Seal: K-40 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 305: Collections in India: Suomalainen Tiedeakatemia.
Comment:
Please note that the elephant motif on the seal impression K-40 a has its head facing left. Therefore, the inscription is read from left to right.
Image Credit:
Indus Script Sign Number 1385: List of Sign Variants: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.