It is worth noting, in addition to the first writeup, that although Devanagari is indeed in rows of five, for the Katapayadi convention the rows are taken in twos, i.e.:

1    2    3    4    5    6    7    8    9    10
ka   kha  ga   gha  ~ma  cha  CHa  ja   jha   ~na
ta   t'ha da   d'ha Na   tha  THa  dha  DHa   na
pa   p'ha ba   bha  ma
ya   ra   la   va   sha  SHa  sa   ha   LA

Knowing this, the naming of ragas such as Dhirashankarabharana makes sense: Dhi-ra, Dhi corresponds to 9 (vowel additions to consonants don't count) and ra corresponds to 2, giving us 29. Further, in order to use the Katapayadi scheme one must know the full name of the raga, as the commonly used name (Shankarabharana for Dhirashankarabharana) usually will not fit into the scheme.