By default CRM is not giving total number of records for entity in grid. If there are more than 5000 records, then CRM will display 5000+ records and when you navigate through 5000+ then count is changing per page size.
If want to show count of total number of records in grid, then need to modify database values.
1. Open MSCRM_CONFIG database in SQL server management studio
select * from DeploymentProperties where ColumnName ='TotalRecordCountLimit'
2. In this table IntColumn default value is 5000.
3. Update IntColumn value to -1
Update DeploymentProperties Set IntColumn=-1 Where ColumnName = 'TotalRecordCountLimit'
4. When using -1, then CRM will take count of all records.
5. If don’t want all records, but want say 15000 records count then update IntColumn value to number of record count want.
6. Reset IIS.
7. Try now..