Oracle Enterprise Manage "CPU utilization" is confusing
That figure is the share of the overall CPU utilization for each process. 

In your case, it means that that specific oracle process is responsible for 100% of your current CPU utilization - i.e., you have no other applications that are eating CPU. So 100% of your ~1-core load is generated by that specific Oracle process.

There is an example in the Monitoring Real-Time Database Performance, and they state it like this:


  In this example, the database is consuming 92 percent of CPU utilization.


So the figure in the top graph shows how busy your cores are, and the figure in the table tells you what part of that load is generated by what process.