Oil & Fuel 3100 Oil Sentry

[JPPWNY]

At 48 hours I changed the oil for the 3rd time since I bought my 3100 tractor.
All was fine until the tractor hit the 50 hour mark today.
The oil sentry light came on and the panel message flashes 'chg oil'.
Oil level is good, the engine runs fine but I have no idea why the panel would be flashing for me to change the oil. Could I have a bad oil sensor? Is there some built in mechanism to warn me to change the oil at certain time intervals? The manual says nothing about this message.

 

[OldMachinist]

From what I understand it's a milestone coded into the hour meter to turn the light on at specified hours and will go off on its own after another amount of time. I've not heard of any way to manualy turn it off.