I too think it's the city of issuance that they are looking for. I just renewed mine as well, and the old passport had the city of issuance as Miami, however the new one doesn't say what city issued it. As a result, I didn't know what to put in that blank. I finally gave up and put "Miami" there, and it seems to work just fine. If they want something else, I'm sure they'll let you know, but I wouldn't loose any sleep over it.