What are the two conventions to identify C in amino acids

Two conventions are used to identify the carbons in an amino acid—a practice that can be confusing. The additional carbons in an R group are commonly designated beta, gamma, sigma , Epsilon , and so forth, proceed- ing out from the alpha carbon. For most other organic mol- ecules, carbon atoms are simply numbered from one end, giving highest priority (C-1) to the carbon with the substituent containing the atom of highest atomic number. Within this latter convention, the carboxyl Carbon of an amino acid would be C-1 and the alpha carbon Would be C-2