If you need clarification on how this pattern works on 84 sts, here are Rnd 6 & Rnd 12 instructions broken down step-by-step (Note: during the twist stitch maneuver there should still be 2 sts in the “twist” -- do not decrease):

Rnd 6 (twist st rnd): K2, p2, T2R, p2, rep from twice, k2, p2 3 times.
Here is that instruction broken down step-by-step:
K2, p2, T2R, p2 = 8 sts
K2, p2, T2R, p2 = 8 sts
K2, p2, T2R, p2 = 8 sts
K2, p2 = 4 sts
(Total of 28 sts)
Then repeat the above actions 3 more times. 28 x 3 = 84

Rnd 12 (twist st rnd): K2, p2, k2, p2, T2R, p2, k2, p2, rep from once, k2, p2 3 times.
Here is that instruction broken down step-by-step:
K2, p2, k2, p2 = 8 sts
T2R, p2, k2, p2 = 8 sts
T2R, p2, k2, p2 = 8 sts
K2, p2 = 4 sts
(Total of 28 sts)
Then repeat the above actions 3 more times. 28 x 3 = 84