Problem with interfaces traffic-graph

[Mehdi]

Hi guys
I have a problem
Today I have add a devices for monitoring traffic , in graph total inbound daily 983 MB but in weekly total inbound is 1.41 GB
Monthly : 695 MB
Yearly : 8.34 GB
What's the difference?
Properly should be equal these graph (for first of the week , month)
Please help me
Thanks a lot