How to use callcounters module to count incoming calls

cdrbuild.conf:

[parameters]
context=false

callcounters.conf:

[general]
parameter=context 
direction=incoming

If there are 3 incoming calls with context=abc and 2 with context=xyz in a new call.route with context=abc it will set:
context_count=3

If allcounters=true then no matter the context in call.route it will set:
context_count_abc=3
context_count_xyz=2