\setcounterformat\rulesseries{#1-#2-#3}{%
  \fcorfinally
  % capitals for chapter numbers:
  \fcformat{#1}{\fcalpha}%
  % digits for section numbers:
  \fcformat{#2}{\fcdigit}%
  % a period to separate section and paragraph
  % numbers:
  \fcformat{#3}[.]%
  % digits for paragraph numbers:
               {\fcdigit}%
  \fcordespair}