This is what I saw first and the reason I was checking on it: Apple has determined that, in a limited number of older generation
15-inch MacBook Pro units, the battery may overheat and pose a fire
safety risk. Affected units were sold primarily between September 2015
and February 2017 and product eligibility is determined by the product
serial number.
The article I saw did not say only those made in 2015 - it said "sold 9/15-2/17" and since I bought mine in 2016, I thought it was reasonable to check. Since mine is not a 2015, I guess it doesn't qualify.
I don't need a new battery. I was only checking because I had a Macbook Pro once that overheated, expanded, and pushed the battery cover off. It was turned off and unplugged, and we were out of town. It turned out it was defective and they gave me a new one. Just glad it didn't catch anything else on fire.
I would still like an answer to my original question which was: are those zeroes or Os? If I have to enter it somewhere else, it would be nice to know. Many manufactures don't use either because it is so confusing - or they only use one or the other. It was a long shot that anyone would know, but that was my question. Thank you for responding.