Verse 7

अत्र ते ये त्रयः प्रोक्ता गुणास्तेऽपि त्रिधा स्मृताः ।सत्त्वं रजस्तम इति प्रत्येकं भिद्यते गुणः

In plain words

Here, those three guṇas just spoken of are themselves each held to be threefold: sattva, rajas, tamas -- each single guṇa divides again into these three.