There are several issues that might be relevant to your numbers here. Firstly, are you looking at CPU usage per core or averaged across all the cores, or even totalled up. For some operating systems (eg. FreeBSD) top will show the total CPU usage. If you have 8 cores, you could have up to 800% CPU usage!
On Linux you can show CPU usage per core by pressing "1" inside top.
Next, you need to think about what CPU usage really means. This isn't a simple concept at all, since CPU usage isn't a meaningful concept at an instant in time. Rather it is a measure of usage over a certain period of time, such as the last second. And running top will itself change the measurement since measuring CPU usage can take quite a bit of CPU itself.
For this reason, another measurement of CPU load is found at the start of the top output:
load average: 1.35, 1.27, 0.72
Here is a useful article which discusses how to interpret load values.