The problem (IMO, not sure if this was what @kentquirk was thinking) is that manually entered SMBGs of any kind are subject to human error. Amusingly, the Tandem software displays for me a huge red display of a manual input BG that I had merely entered wrong on first try (it was 230, not 23):
![screenshot 2014-05-27 08 17 26](https://cloud.githubusercontent.com/assets/1588547/3093398/14dc8b92-e5b2-11e3-993d-377806456380.png)
We want to be able to identify these clearly so that the user is not unduly alarmed (as I was the first time I saw this 23, which prompted me to investigate in my raw data).