The Indus Dictionary Project
This is a pictograph of a mat with each short edge split into three units. It therefore denotes a floor or pitch area with a width of three standard mats. In addition, the centre of the mat is marked with three counting rods, which indicates that the length of the area was also three mats.
Mohenjo-daro: Seal: M-637 a: Sayid Ghulam Mustafa Shah and Asko Parpola, 1991: Corpus of Indus Seals and Inscriptions: Volume 2: Page 21: Collections in Pakistan: Suomalainen Tiedeakatemia.
There is only one extant example of this Indus sign.
Perhaps the floor layout was something like the diagram on the right. The notation in Mahadevan's sign number 1034 may have been used to avoid confusion with sign number 4002, which is a three by three crate.
Indus Script Sign Number 1034: List of Sign Variants: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.
Nine Mat Floor: Lynn Fawcett, 2017.