Fanuc control machine timers-help to understand

To start off with, I know that the timers accessed within the control are re settable and do not necessarily represent actual total machine use time. For my question, lets presume that the timers do not get reset.

I have 3 machines that are using Oi, 16i, and 31i series controllers that I am looking to track time of use from week to week; how much the machines are being run.
All three machines have a RUN time counter that is displayed on the main screen while the programs runs. I am also aware of parameter 6750-6754 timers; available on all three machines. Does anyone know how the run timer is calculated? Is it similar to PARAMETER 6753 CUTTING TIME?

Also, does anyone know if the cutting time in parameter 6753 rolls over and starts again? For example, one machine was at 54160 cutting time last week and this week it displays 17056 cutting time; doesn't make any sense and I am about 99.9% sure the parameter was not reset by any of the operators.

Any help shedding light on these timers and parameters would be helpful.

Looks like Fanuc uses two parameters to keep track. 6753 & 6754 together keeps tracks of the total time. See attachment.

I guess it took someone to post what was in front of my face the whole time in order for me to see it. Now that I have read instead of glossed over everything, it clearly states that 6753 unit of measure is milliseconds and 6754 is minutes, so I was even looking at the wrong parameter. In my haste, I was just looking at them as two identical timers and obviously not reading everything.

Thanks for the reply drdos!