The In and Ready Address Spaces report has been replaced by the CPU Queuing report. The CPU Queuing report shows similar information, but with more detail and takes into account the number of CPUs available.
The report description is retained here for historical reference.
This chart shows the average number of in and ready address spaces in the system. In and ready address spaces are either using CPU, or waiting for a CPU.
This is a simple indication of the amount of CPU contention.