“Known” in Chinese Toolbox should not be taken absolutely and literally. It is obvious to anyone who has studied Chinese that rarely if ever can you just know a character. Most Chinese characters are complex, and there are many aspects of knowing a character. Marking a character as Known in Chinese Toolbox does not mean that you know everything about a character, but rather that you are learning to read the character. Marking characters or words as Known is like a little nudge to help or remind you to exercise yourself mentally to try to understand the character or word in whatever context it exists. And don’t forget that you should be using the keyboard to read those characters and words that have been marked as Known.
For the sake of the Chinese Toolbox interface and documentation, some word had to be chosen to represent this concept. “Familiar”, “Recognizable”, and “Understand” were all used in earlier versions of Chinese Toolbox, but eventually “Known” was chosen mostly because it was the shortest word, and it was the easiest to incorporate into the interface.
The 2007 and 2009 versions of Chinese Toolbox used five levels of Knowing; at the time it was called Understanding Level. The code for these “levels” still exists in Chinese Toolbox, though for now it is not used. It will be resurrected in an upcoming version of Chinese Toolbox where you will be able to designate degrees of understanding, or “Known Levels”. This resurrection is dependent on the development of a new system of review, which is being developed with new mobile versions of Chinese Toolbox.