I want to assign the function key 1 to line 1 with context (called "number" at the snom webinterface) <sip:4@sip-server;user=phone>

Unfortunately the device wont set this value, if I assign it via SRAPS:

Instead there is only a "1" in the numbers field, when I look at the function keys site at the web interface of the phone.

How is the correct syntax for this to work?