If I Enter a new advanced file mapping via 'Document - select Mode' the pattern inserted by SE contains &3105.
Please have a look at the screen recording attached: I tried to map Kconfig Mode to all files named Config and SE made an entry '&3105Config'.
OS Version: Ubuntu 16.04.2 LTS
Kernel Level: 4.4.0-87-generic
Processor Architecture: x86_64
Regards
Exo