Silly question - how to preset radio stations?

I'm sure the question is silly, and as no-one else asked, everybody seems to know (or doesn't use the radio?), but - how do I store radio stations to the various presets? I can easily change frequency, but when I then press "next preset" and "previous preset", the frequency has reverted to some old value. Also, how many presets are there? And, although it's not documented, the number keys on the remote seem to jump to a preset directly - is that true?

Press DNPP on the remote then the preset number you want to store in. There are currently 10 presets, 0-9.

Hugo