The Dashboard page of the web UI reports CPU load and Throughput, but does not say when this refers to. My guess is that it is the last 10 seconds as it refreshes itself on roughly that schedule. Whatever timeframe this data applies to, should be specified on the Dashboard page.
The same applies to the client list page (on the Status tab) which shows download and upload bandwidth for attached devices. Here too, the page does not report the timeframe involved. That is, it should say that the reported bandwidth is for the last X seconds, whatever X is.