Hi Krish,
The url you are providing for dynamic count is not correct.
You need to append $count in the end of url used to get entity set.
/sap/opu/odata/sap/<odataservice_name>/<entityset>/$count
IF still you are not able to figure it out, please share metadata call response of this odata service.
/sap/opu/odata/sap/<odataservice_name>/$metadata
Regards,
Sarbjeet Singh