Need help to understand ServerStatus Daily Process Log %


Dec 3, 2010
My problem:

Server was extremely slow and I reported that problem to my hosting. Later I received notification from my Shared cpanel hosting provider that my account is using too much CPU.
They sent me few screenshots from "Server Status > Daily Process Logs" page displaying %CPU usage for my account ~8%.
One screenshot was for the day server become slow, however others were from time server operated fast, so I believe that my site did not cause overload.

Anyway my site should be using no were close to that much CPU.
I wrote a script to get server stats (with exec('uptime')) and send that info to me every few minutes.
I collected info for past day but it never shows more than 4% CPU usage and most of the time CPU usage was less than 1%.
Question I must ask
How is it that Server Status > Daily Process Logs shows 8% just for my account alone when data I got with exec('uptime') indicates that all server CPU usage combined should be below 1%?
Is it possible that Server Status > Daily Process Logs does not show overall % of CPU capacity usage, but given account's contribution % of CPU resources used by all accounts?
Cause my observation can only make sense if all server used ~1% CPU and mine account is responsible for 8% of that usage.