How to train Double-Take to better identify "Unknown" people?

[guttermonk]

Double-Take does a decent job of correctly identifying people, but every once in a while it detects a stranger and identifies them with a high degree of certainty. If Double-Take detects a name incorrectly, is there a way to add it to the training set as unknown?

I'm sure I may just be missing something, but it's not clear if I should add "unknown" in the "add new" drop-down and then use the Train button to add them to the training set as unknown, or how to go about doing this. Seems like that should be an option by default. Any suggestions on how to train Double-Take on who strangers are?