From the Nova Max Glucose/Ketone meter user manual, page 34
If the blood ß-Ketone result is
between 0.6-1.5 mmol/L and glucose is more than 250 mg/dL, this
may indicate development of a medical concern. You need to contact
with your heathcare professional for assistance.
If the blood
ß-Ketone result is more than 1.5 mmol/L and glucose is more than
250 mg/dL, contact with your heathcare professional immediately.
This indicates a risk of developing DKA.
So it sounds like a 0.6 is a cause for concern but not DKA development.
I would get more water into Bob if you can. Water helps to flush out any ketones. Since he refuses to eat the wet food, you may need to syringe water into his mouth or get fluids from the vet and give him some fluids sub-q.