Ta is the sixteenth consonant of Indic abugidas. In modern Indic scripts, ja is derived from the Brahmi letter after having gone through the Gupta letter .
Aryabhata used Devanagari letters for numbers, very similar to the Greek numerals, even after the invention of Indian numerals.The values of the different forms of त are:
References
Ta (Indic) Wikipedia(Text) CC BY-SA