I’ve got a refurb t-slim, sent as a warranty replacement (I actually think it’s my fault I screwed the first one up.). My serial number starts with #90, not 99.
I wouldn’t be worried about the refurb thing. My experience with this one has been great. I couldn’t tell any difference from when I opened my brand new one… Except, like @El_Ver said, this one works better.
Electronics have quirks sometimes, that can be fixed, and made like new. Buying refurb is an excellent way to get thoroughly tested and just-like-new equipment for a better price. Keeping the cost of healthcare down, means more care can be made available to you. As in, you were able to choose the pump you wanted, rather than being forced into whichever one Medicare could barter for cheapest (like the preferred drug list).
If ever the pump doesn’t work correct, customer service is really great at sending a replacement. I didn’t get same day service because my pump didn’t throw any error codes for them to verify a problem, it was mostly my gut telling me things weren’t right. Instead, it took two days. All they asked was that I get a second opinion. They had a diabetes educator contact me, and took her recommendation, then overnighted the pump. I was thrilled to death that they were willing to work with me without any malfunction code!