The letters stand for the 7 swaras in Karnatik Music.
s for saa
r for ri
g for gaa
m for maa
p for paa
d for daa
n for ni

Traditionally, the notations are written using small and capital letters, commas and semicolons.
s (small letter) 1 unit 
S (capital letter) 2 units
, (comma) 1 additional unit
; (semicolon) 2 additional units
*units are called aksharakalas*

But for the sake of convenience, we have only used small letters and commas.

Instead of using dots for denoting the octaves, we have tried using different font colours-
Red swarams are for higher octave (Taara sthayi)
Black swarams for middle octave (Madhya Sthaayi)
Blue swarams for lower octave (Mandra Sthaayi)

The | and || signs are to show the sections of the talam.