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As others have said, get a copy of the actual lab results, but keep in mind that any notes or references to the numbers on those results will be "dog" not greyhound. I would very quickly find a good greyhound vet and make an appointment for your girl and bring in all test results for a second opinion. As many greyhounds as there are in California it shouldn't be hard to find a good vet, consult with the group you adopted from. Continue to give the antibiotics until they are all gone. Two weeks after the antibiotics are complete have her urine re-tested. UTI's are not that uncommon and I would prefer to err on the side of caution. Having complete bloodwork done on an 8 year old annually is totally appropriate. Not knowing what all was done for the $377. it isn't possible for any of us to comment on you being taken advantage of (or not), plus prices vary widely throughout the US. Check these links out for greyhound recommended vets in California, hopefully one will be near you.
Greyhound Connection
Greyhound Adoption California