It isnt a measurement of visits. It is how many resources is being consumed. Such as a proxy site or large databases. They put large strain on the cpu (processor). You site is consuming 28% of all resources. The server you are on has 2 cpu's, so you are using 14% of resouces on each. I would also consider that high even @ 14% and 2 processors.
So, if it is one of those sites, it could be just a small handfull of visitors. They are working the server hard. Doings this leaves little for other users and give slow server response or load time.
RickyG