CC Madhya 24.288
vidhi-rāga-mārge cāri cāri — aṣṭa bheda
jāta-ajāta-rati-bhede — by distinction of mature love and immature love; sādhaka dui bheda — those practicing devotional service are of two varieties; vidhi — regulative devotion; rāga — spontaneous devotion; mārge — on both the paths; cāri cāri — there are four different varieties; aṣṭa bheda — a total of eight kinds.
“Those who are practicing devotional service are either mature or immature. Therefore the sādhakas are of two types. Since the devotees execute either regulative devotional service or spontaneous devotional service and there are four groups within these two divisions, altogether there are eight varieties.