Hi Michael,
that's exactly what i have mentioned by "or the data basis (how and when are the values or metrics incremented / measured and populated) is not known."
However you can calculate the correct CPU usage with other metrics (even for a one hour snapshot) - for example:
The CPU time recorded in the "Top 5" as accumulated at the end of a database call. The DB CPU reported in the "Time Model" stats is incremented every few seconds.
...
You can see that the total CPU used over the two reports is about 181 seconds, but the "Top 5" sees none of that until the query completes. The "Time Model" stats report the split of CPU usage across the sessions.
Source:https://forums.oracle.com/message/2573383#2573383
The problem with a larger AWR report time scale is, that you can not break it down to the mentioned time frame properly (it will become very incorrect by increasing the time scale) - you just can calculate averages over 3 hours or so (by using the AWR report).
Manual queries on ASH are always possible for getting the details :-))
Regards
Stefan