Dear , Majid becuase as you know SDCCH is a control channel the user and network use this channl for many thing
location upadte , IMSI deatach,
recall estiblshed ,, sms ,,so try to check the defination of this KPI,attempted sdcch seizures all
which services are include in this counter , you have to know the traffic from whaere
also check your resourcse .