Just found out the manufacturer: It's Aikotec (
www.aikotec.com).
As as I thought the device is only designed to handle 5 devices. So the calculation computes: 50 keys * 5 devices = 250 possible commands.
I don't know why it's advertised that this remote control can handle 15 devices. Possibly because you could share one button set for 3 devices? With such a calculation the web shops could even say that this remote handles 250 devices - one button each... ;-)
(:Clemens:)