From looking at your webpage it looks like you've got the 315 which is a little fancier than the 310 [btw, the motorcycle mount is really cool!]. I double checked your directions just be be sure and the 310 does not support displaying dd.mm.mmm notation. Unlike the 315, the 310 has a segmented number display (like on a digital clock) and doesn't have enough space to display that many digits.
I have noticed however that the 310 keeps track of more decimal places internally. It outputs 4 decimal places to the minutes when it is connected to a computer.
Overall, I'd say that the 315 is probably worth the extra $40 since it has a better display and quite a few more features.
Adam > Hi! Adam!! > I think you can change the coordinate system on the 310, you may have > it set on degrees/minutes/seconds or degrees/minutes/mm > Try this and you may be able to reset it: