Anyone know what resets the device usage power report?

[WBFAir]

Hello all

Over the past few days I have left my TP2 on overnight twice and it has completely drain the battery to the point it shut itself off and wouldn't even allow me to restart it in the AM for more then the time it tells me that the battery is very low before it self shuts down again.

After that I then plugged the device into the wall charger with it off and let it recharge till I had a green light again.

In both cases I checked the Settings>Power>Information report and while it does give the correct date and time for the "Last full charge" part, all the other usage info under the "Since last full charge" part has been just accumulative, in other words it is not actually showing the usages from the “Last full charge” date and time that even it lists, but all the usage times for for a while now.

So does anyone know what might reset that back to the last full charge time when it has completed its last full charge or could recommend anything else that they think I am doing or is wrong?

Thanks