I would trust my built in gas detector (nose), before an electronic sniffer. Yes, I use to have one as just about every new home inspector. They are very very sensitive and will produce false positive readings. Your breath will cause some to start alarming. I even had them go off at high concentrations of CO when a device was fired up.
The area you tested looks like the vent for the oven. If the oven was just turned on it could be from the left over gas or high CO.
If you did not smell it with your God given detector, I would not worry about it. But since you posted this on a public board that everyone can see, you might want to make note of it in your report!
