In the default FreeSWITCH configuration ("vanilla"), dialplan/default.xml
contains <extension name="Local_Extension">
which matches 4-digit numbers starting with 10. That's why your 516... numbers do not match.
I would advise to start with the minimal configuration (https://github.com/xlab1/freeswitch_conf_minimal) and build your dialplan as required. The default configuration has too much stuff which needs to be removed.