I wanted to know what the update inferval means because I changed it from 1 to 10 and back, but there's no change. Does it mean 1 being less time or 10 being more often?

This is actually a problem with netstat, not the widget. netstat can only handle number of up to 4GB. That means when you go over 4gb in or out, the counter will flip over back to 0. This will be fixed in my widget in future versions.

Just downloaded the widget today and within 5 minutes of starting it the Down Today Portion is displaying a negative number. (i'm in the middle of copying about 50 Gigs from a file server) I started the widget to monitor my speed, which it does wonderfully. (while typing this the number "rolled-over" and is now displaying ~400MB downloaded.)
Overall does what I want it to do.

This widget uses a utility called netstat to get usage statistics. Some version of netstat is included with all operating systems (Windows, OS X, Linux, etc...). Netstat records internet usage from the last reboot. This is why the widget resets on reboot. It would be possible to create a widget that never reset, but there are all sorts of usability problems with this (I built a widget that did it and never released it for this reason).

why does it reset the totals when i restart my computer?