Greedy Scheduling in Multi-threading programming in cilk

Question

I am having problem understanding the complete step and incomplete step in greedy scheduling in Multi-threaded programing in cilk.

Here is the power-point presentation for reference.

Cilk ++ Multi-threaded Programming

The problem I have understanding is in from slide # 32 - 37.

Can someone please explain especially the how is

Complete step>=P threads ready to run
incomplete steps < p threads ready

Thanks for your time and help