How to entry the malfunction of ODME in Oil Record Book Part II?

Dear all,
The printer of my vessel’s ODME was failure so that I had made entry of code M into Oil Record Book Part II. Later, the printer was fixed by Electrician. And then I carried out the function test of ODME system (simulation only) and tried out the ODME system in IDLE Mode to verify the operation of printer. With this action, I’ve made entry of code O for testing the ODME system but now I confuse Code M (M.71) or code O which are the correct entry for this case.
Many thanks for your wise advice.

In my dealings with the USCG, they are less concerned with the codes than the accurate description of events. Make sure times, dates, and events are accurately recorded. Get the pertinent info in the book and nobody will sweat the codes you used. Just do the best you can. Any of those codes will result in a second read from an inspector. The USCG’s biggest issue is lying to them. If the truth is in the book. No worries about the proper codes.

Falsifying the book is what any port state control looks for. My goal is to never run the OWS except to show it works for PSC. I worked in Europe in the Baltic on a container ship and part of our port fees paid for getting rid of sludge and bilge water. I could order a barge or truck in most ports at no cost to us as we had paid it anyway. It should be maritime law that every port has to provide a means to take waste water and oil from any ship, anytime as part of the vessels port fees.

Is there anyone can give the more detail answer?