1. Correct, the value is = (current counter value - previous counter value) / poll interval in secs.
2. The timestamp indicates the end of the period, i.e. the second line refers to 9:03:28 and 9:08:28.
3. Correct, the bytes indicate the traffic volume in a respective minute.
4. The timestamp indicates the beginning of the period, i.e. it indicates the respective minute. So the first line refers to the minute between 7:59:00 and 8:00:00.
Thanks a lot for your reply :-)