Cpu processes always at 39-41% in RRDGraphs

[b4nsh33]

Hi, i think the rrd graphs are not showing correct values regarding the cpu usage, because user , nice ,system and interrumpt are always below 6%, but cpu processes always shows 39-41%, in status -> system and running top from a console i have never seem more that 4%, from where is rrd getting that high value from processes?
regards