The RC divided by the number of decks remaining.
With 6 decks, 3 decks dealt and an RC of +6, the TC is +6 ÷ 3 = +2. The fewer cards remain, the stronger the same RC is, so you need this conversion. Round it down (+2.7 → +2, −0.5 → −1). Example bet guide: 1 unit at TC +1 or less, 2 at +2, 4 at +3, 8 at +4 or more.