How does the % function work?

The general idea is gret. I dont even have an issue with the two-finger clear gesture. But I cant for the life of me figure out how to use the % function (so much for "intuitive interface"). Unfortunately the "Tech Support Site" does not seem to have any means to send feedback or questions. Altogether I agree with those who have said that this is a good idea in development, not quite a finished product.

Gekkosan about Rechner Calculator