This is a pictograph of a measuring rod. There are four spaces which gives us four units of measurement.
Illustrative Text References:
Four units - height: Mohenjo-daro: Seal: H-584 a: Sayid Ghulam Mustafa Shah and Asko Parpola, 1991: Corpus of Indus Seals and Inscriptions: Volume 2: Page 294: Collections in Pakistan: Suomalainen Tiedeakatemia.
Four units - width: Mohenjo-daro: Tablet: M-1425 A: Sayid Ghulam Mustafa Shah and Asko Parpola, 1991: Corpus of Indus Seals and Inscriptions: Volume 2: Page 193: Collections in Pakistan: Suomalainen Tiedeakatemia.
The verb to measure: Mohenjo-daro: Seal: M-704 a: Sayid Ghulam Mustafa Shah and Asko Parpola, 1991: Corpus of Indus Seals and Inscriptions: Volume 2: Page 42: Collections in Pakistan: Suomalainen Tiedeakatemia.
The noun duration: Mohenjo-daro: Tablet in bas-relief: M-1419 A: Sayid Ghulam Mustafa Shah and Asko Parpola, 1991: Corpus of Indus Seals and Inscriptions: Volume 2: Page 191: Collections in Pakistan: Suomalainen Tiedeakatemia.
The noun length: Harappa: Tablet - incised: H-1319 A: Asko Parpola, B. M. Pande, and Petteri Koskikallio, 2010: Corpus of Indus Seals and Inscriptions: Volume 3,1: Page 170: New material, untraced objects, and collections outside India and Pakistan: Suomalainen Tiedeakatemia.
The adjective lengthy: Harappa: Seal: H-1077 a: Asko Parpola, B. M. Pande, and Petteri Koskikallio, 2010: Corpus of Indus Seals and Inscriptions: Volume 3,1: Page 148: New material, untraced objects, and collections outside India and Pakistan: Suomalainen Tiedeakatemia.
Comments:
Although, the literal translation of Mahadevan's sign number 1046 is four units of measurement. In practise, it was often used in a more general sense to refer to measurement and length.
The purpose of seal M-704 is not clear. However, it is possible that Mahadevan's sign number 1046 was used as the verb to measure rather than referring to four units.
Inscription M-1419 concerns distance and time. Unfortunately, photograph A is not completely legible. However, it may be that Mahadevan's sign number 1046 should be interpreted as duration rather than a specific number of units.
Image Credit:
Indus Script Sign Number 1046: List of Sign Variants: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.