Oh neat! The cams (those discs) hide behind the dial!
I'm guessing the numbers on the dial match up to the numbers on the cam; so you find the pattern you like, look at the number, and then place the cam with the matching number into the machine...?
The R button probably is reverse; the "L M R" dial is left, middle, right needle position plus some buttonhole positions. The other dial looks like stitch length. No idea what "tri-cycle" means!
Looks like a great machine! Congrats on the find, and welcome!