I can't say with 100% certainty, but I believe this is just a documentation error on the page. The limit should be removed in the software itself. I believe there is a bug filed to fix the wording on that page.
Also of note, all of the APIs are tested and working (except for i2c). Things are looking good for a beta release near the end of the month!
It looks like it is working to me. The 50Hz mains power is capcitively coupling into the ADC input, therefore you see a 50Hz sine wave in the graph window. The noise on the sin wave is due to the fact that this signal isn't really being driven with any strength. If you were to pick up the signal with an antenna and then buffer it with an opamp before sampling, I would venture to say that the sin wave would be much more ideal.