cacti graph daily view and moving backwards question

Hi,

Using <-- or --> and dropdown is set to "1 Day" to see the traffic per day without changing the aggregation, does cacti aggregate the data for the previous days (specifically 3 days before)? Seems like it does because for example the traffic for today and previous day seems the same but going further back (clicking <--) the traffic shows smaller and the lines in the graphs starts to look thicker.

Any idea?

Thanks,
Mon
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