Thank you Paul for the suggestion to change the priority of the core switch to 0.
We have done that made core switch as priority 0.
when i get the show spanning-tree output, i can see that the topology change count still changes i have pasted the output below.
sh spanning-tree
Multiple Spanning Tree (MST) Information
STP Enabled : Yes
Force Version : MSTP-operation
IST Mapped VLANs : 1-4094
Switch MAC Address : 9cdc71-04c27f
Switch Priority : 32768
Max Age : 20
Max Hops : 20
Forward Delay : 15
Topology Change Count : 2,060,101
Time Since Last Change : 40 secs
CST Root MAC Address : 9cdc71-04c27f
CST Root Priority : 0
CST Root Path Cost : 0
CST Root Port : This switch is root
IST Regional Root MAC Address : 9cdc71-04c27f
IST Regional Root Priority : 0
IST Regional Root Path Cost : 0
IST Remaining Hops : 20
Root Guard Ports :
Loop Guard Ports :
TCN Guard Ports :
BPDU Protected Ports :
BPDU Filtered Ports :
PVST Protected Ports :
PVST Filtered Ports :
Root Inconsistent Ports :
Loop Inconsistent Ports :