First let me say that if you had posted your question as new, you might have had more responses to your question. It seems to have gotten lost here posted with another question.
bptr dec = back post treble decrease -- (called Treble Decrease) -- Work a treble in the next stitch (without completing the last step) Work a treble in the next stitch (without completing the last step) Now yarn over and draw through all loops on the hook.
(called Treble Next Two Stitches Together) -- Yo twice, insert hk in next st, yo & draw through lp, yo & draw through 2 lps, yo & draw through 2 lps, (2 lps on hk)yo twice, insert hk in next st, yo & draw through lp, yo & draw through 2 lps, yo & draw through 2 lps, (3 lps on hk)yo and draw through all 3 lps.