So for reference, you can get the CPU load average of the hub, if you so desire.
http://<hub_ip>/hub/advanced/cpu1min
http://<hub_ip>/hub/advanced/cpu5min
http://<hub_ip>/hub/advanced/cpu15min
There's also a community made driver that collects similar info and consolidates it for you, if you so desire.
The stats, as reported on the apps and devices pages are reporting the amount of time those drivers or apps have run. If you're resetting the counters and the values are quickly increasing, it sounds like you have a device that is running constantly and possibly out of control. The percentage you see is amount of time running / total system uptime (this total uptime might reset when you reset stats). That percentage has nothing to do with CPU use.
For example, on my hub device drivers have run for a total of 24 seconds of a total uptime of almost 6 minutes (I just reported the hub).
