I'm not sure what you're asking about here. "Multi-compare" is a way to add multiple users in the compare-tools. For example you could use MapCompare to add the four people you are going geocaching with and then select the "None found" to help plan the trip.
In StatCompare you can add multiple profiles to compare your stats with, but I'm pretty sure the tool would break if you add every geocacher on the planet to the tool. I don't know what the upper limit is, but I'm sure there is one.
To set the tool in "multi-compare-mode" you click the right part of the "compare with"-box that looks like a list and then you can add multiple accounts to compare with.
