Why only 8 numbers in indian numerology?

Every number is magical, this thing was also known by Pythagoras. There are various systems to couth maybe birth date, or name. There are various interpretations and systems for letters of alphabets, or some similar meanings. We know also 9 numeral latin alphabet system, Abjad countains also numbers with zeros, Chinese (mainly Cantonese) have also nine number systems by similarity of the word in this dialect.

But what? There is also numerology systems in the indian (specifically Tamilnadu)? But, with eight numbers only? I understand, if zero (0) isn’t presented, because 0 is beginning of everything, but why nine? By my intuition I have noticed some things. For example, if We have overtones at music, multiple of eight is same, like fundamental. It means, that if fundamental is c, eight overtone is also c. Nextly, letters of this indian numerology is very different, like We know from latin alphabet. Also, there isn’t possibility to count birth date, because nine is missing. There is also one thing to remember, that mostly brahmi scripts have sort of letter by creation of sounds (phonetic). Because of contacts with foreigners, indian numerology system is optimized specifically for latin alphabet, but maybe not logically at all, maybe mostly intuitive. Question is, why eight numbers, not nine?

By my way I think this: Indians creator gets also inspiration, when they create this numerology system from music, because by indian philosophy is music very common with math. Ofcourse, It is also another possibility. Result of 1*2 is 2, 2*2=4, 4*2=8, those overtones are octaves in musical therminology.