Hi!!
Below is description for counter you mention:
CCS_UNANSWERED
Purpose
This counter registers the number of calls that, after being successfully connected
through switching network, are rejected because either the called device did not answer
or the calling party went on-hook during ringing.
Trigger at LTG error
The counter is triggered when the LTG reports the following RCF.
RCF#016 : RF_NORMAL_CALL_CLEARING
RCF#018 : RF_NO_USER_RESPONDING
RCF#019 : RF_NO_ANSWER_FROM_USER
RCF#020 : RF_SUBSCRIBER_ABSENT
RCF#028 : RF_INVALID_NUMBER_FORMAT
RCF#145 :RF_OPR_ABANDONED_CALL_DURING_DIAL
RCF#147 :RF_CREDIT_LIMIT_EXCEEDED_D
RCF#153 :RF_CREDIT_LIMIT_EXCEEDED_A
RCF#157 :RF_CTX_NON_FAILURE_REROUTE
RCF#159 :RF_CTX_CAMP_ON_UNSUCC_NO_REPLY
RCF#179 :RF_SUB_FREE_TRUNK_OFFER_REFUSED
RCF#183 :RF_CALL_ABAND_AFTER_FIRST_DIGIT
RCF#233 :RF_CALL_DIVERSION
Best regards!