A ketone reading of .02 is still low. I'm presuming you're testing for blood ketones. Ketones aren't worrisome until they are testing at around 2.0. This is information on ketones and DKA.
If you consider what happens if humans start a high protein (i.e., keto) diet, their level of ketones may increase. That doesn't mean that it's dangerous. It's a reflection of diet. For a cat that is eating a low carb, high protein diet, it's highly unlikely that ketones would be zero. We get truly concerned if blood ketones are at around 2.4 or more of if you're testing for ketones in the urine, if the level is above "trace."