deriv LSK ETT STT aSTA ALPH OLDHOMEPAGE NEWHOMEPAGE
Rule jhalAJjazjhaz... literally says "Replace serious with j b g D d before voiced stops".
Then next rule abhyAsecarca says "in the abhyAsa with c T t k p z S s as well"
So abhyAsecarca actually means "replace serious of an /abhyAsa with j b g D d c T t k p z S s".
This will obviously replace the consonants j b g D d c T t k p z S s with themselves.
The remaining serious are h ह् and jh झ् bh भ् gh घ् Dh ढ् dh ध् Th ठ् th थ् kh ख् ph फ्.
The h ह् never appears in an /abhyAsa because kuhozcuH replaces it with j ज्.
Therefore this sUtra will only replace jh झ् bh भ् gh घ् Dh ढ् dh ध् Th ठ् th थ् kh ख् ph फ्, each one with the most alike of j ज् b ब् g ग् D ड् d द् c च् T ट् t त् k क् p प्.
My head hurts. Why didn't /pANini just say "replace /jhay of an /abhyAsa with /jaz /cay" instead? That would have been simpler.
Simpler yes, shorter no. See /ardhamAtrAlAghavena.