Hi,
If you read the mouse over for the two setting you will get all the technical info. Personally I have never adjusted these setting and have stacked and processed images on PC's with 8GM ram and 1 processor (2 cores) and a high-end server with 64 GB RAM and 2 CPUs (16 cores). Sometimes it takes more time and effort to fiddle with the setting ... rather just accept the defaults and use the time to have another beer ..... Good luck.
Look up
John