Memory used by user processes and kernel (excludes buffers-cache) (ActualUsed)
This attribute reports the percentage of (logical) free memory available for use by applications on the system rather than the real free memory on the system. It includes the real memory consumed for file-system buffers and page cache.
The Solaris systems allocate free memory dynamically for use by file-system buffers and page cache rather than wasting the physical memory. Whenever applications need more memory, the memory used by buffers and cache is allocated for use by applications. Hence, the memory consumed by buffers and cache is treated as free memory rather than used memory, on these systems.