The D5G has one Electronic Control Module that controls and monitors the Hydrostatic system. The exclamation point lights up to indicate that the ECM has detected a fault in the Hydrostatic Electronic Control System. If it came on and went back out in 10 seconds, and if you did not hear an audible alarm, it was likely a momentary signal loss, just a "glitch". Next time you are at your Cat dealer, or they are out working on the machine, they can hook up Cat Electronic Techinician and tell you what fault was logged. If it continues to happen, or if it comes on and stays on, or if it comes on along with an audible alarm, you should get it checked. If it does not happen again, it was probably just a glitch and won't cause any problems.
There is a procedure to check fault codes without Electronic Technician but it involves jumper wires, counting the number of times the light flashes , etc. and is not really worth the effort.