The one CA is nothing to worry over. As Dave states, unless you see lots of them on a consistent basis, it's not a problem.
It's not caused by using EPR 2, as in your case with low pressures, EPR doesn't kick in until your pressure reaches 6cm.
Also, even though your overall leak rate is not that high, it seems consistent throughout the night. It looks like a combination of mouth breathing and mask movement. Visibly line of the leak graph with the time of the CA. Do you notice the higher leak rate at that particular time? That single CA is probably related to leaking or movement. Again, don't fret over that, instead concentrate on mask fit and possible mouth breathing/leaking.
Eventually, please consider a slight pressure adjustment to be able to utilize EPR better. (This will help you breathe out easier against the pressure.)
Try this experiment.... Stay with the Auto Pressure mode, but set the minimum pressure to 6.4 and the maximum pressure to 6.4. Set EPR to 2. (Work you way up to 7-7 with EPR 2) Your apnea is mild, and this should prove very comfortable.
The next time you post a chart, include these graphs:
Events, Flow rate, Pressure, Flow Limitation and Leak rate.
In answer to your question...
"is there a way to switch oscar display to standard time instead of military time?" No
At your leisure, start reading through the
OSCAR Guide.