siddha-sādhya-susiddhāri- kramāj jñeyo vicakṣaṇaiḥ

siddha-sadhya-susiddhari-
kramaj jneyo vicaksanaih

These are (1) siddha, (2) sadhya, (3) susiddha and (4) ari. These four principles can be divided further: (1) siddha-siddha, (2) siddha-sadhya, (3) siddha-susiddha, (4) siddha-ari, (5) sadhya-siddha, (6) sadhya-sadhya, (7) sadhya-susiddha, (8) sadhya-ari, (9) susiddha-siddha, (10) susiddha-sadhya, (11) susiddha-susiddha, (12) susiddha-ari, (13) ari-siddha, (14) ari-sadhya, (15) ari-susiddha, and (16) ari-ari.

Those who are initiated with the eighteen-alphabet mantra do not need to consider the above-mentioned sixteen divisions. As enjoined in the Hari-bhakti-vilasa (1.215, 219, 220):