General bandwidth question

[highlander]

Hi All,
I'm sure there's a fairly straightforward answer to this but why when I'm downloading a file at say 1.5mbps does my firewall (and therefore cacti) report the interface traffic usage much higher at 20mbps+

I know this isn't specific to cacti but figured someone here would know the answer.

Thanks in advance!

[victorantunes]

Please post a screenshot of your graph.