The understanding script can understand simple phrases of the form "noun - verb - adjective" or some variations.
For the bot to understand it must know what type of word it is, the bot will load word data from Wiktionary as it encounters new words. The first time the bot encounters a new word it will not understand, but it will load the word data from Wiktionary in the background so that the next time it will understand the word. Some words such as names it may not find on Wiktionary, although Harry appears to be there.
Also ensure you don't have learning enabled as this will have the bot learning your responses, so you will end up getting your own response back.
Log from new "basic template" bot.
is snow white
Sorry, I do not understand, perhaps rephrase your question.
is snow white
I'm not sure if snow is white.
snow is white
I understand, snow is white.
is snow white
That's right, snow is white.
is Harry sleeping
Sorry, but I do not understand.
Harry is sleeping
I believe you that Harry is sleeping.
is Harry sleeping
Yes, to my knowledge Harry is sleeping.