IP BASE - Why is the number of an incoming call shown twice in the display?

This is basically correct at this point and corresponds to the implied CAT-iq 2.1 standard where additional information (CNIP) can be displayed besides the phone number (CLIP). More and more providers support this function, but even if you use a router telephone book, this additional information is also sent to the connected devices in addition to the telephone number. If no CNIP is transmitted, the phone number is displayed at this point.