I have an 04 Accord LX v6 nav and I was holding down the odometer button to reset the maintenance required light and I noticed the trip-odometer display started counting 0, 1 ,2 ,3 ,4 ,5, -5, -4, -3, -2, -1,0 and back again. What does this mean or what does it do?

 

I think you were adjusting the outside temperature reading. From the numbers you posted, I assume you can adjust it up or down by 5 degrees. To reset the maintenance required light: Key turned off, push the reset button with your left hand, continue to hold the button down and turn the key to on (no need to start engine). Hold the button down until the light goes out. Look at the little dimple in your finger, from holding the button down so long.

 

Yep, outside temperature display adjustment feature.