P/S ratio - what is the (1-b)?

There was earlier confusion as to the inputs in the numerator of the P/S ratio. Is the (1-b) saying that “b” is the payout ratio? Therefore 1-b is the Ret Rate? Or does “b” stand for Ret rate and we use 1-b to get the Payout ratio in the numerator? Thanks in advance for any clarification.

1-b is the payout ratio, b is retention