T-4x Provisioning : linekey.x.pickup_value

Hello,

I have the following in the configuration file :

linekey.4.line = 0
linekey.4.value = 10
linekey.4.pickup_value = **
linekey.4.type = 16
linekey.4.xml_phonebook =
linekey.4.label = 10

I notice however in the webinterface of my Yealink T-46G that for linekey 4 the field "Extension" is empty (in stead of holding the value '**').

How do I fill in the last field "Extension" of the line key via provisioning ??