How many signs are estimated to be present in the Harappan script?

Between 375 and 400

Harappan seals typically bear a line of writing, possibly indicating the name and title of the owner. The motifs, often depicting animals, are believed to convey meaning to those who could not read. Inscriptions on these seals are generally brief, with the longest containing approximately 26 signs. Although the script remains undeciphered, it is evident that it does not follow an alphabetical system, as it comprises a significant number of signs, estimated to be between 375 and 400. The writing direction appears to be right to left, as indicated by seals exhibiting wider spacing on the right and cramped spacing on the left, suggesting the engraver started from the right and ran out of space.