It is variable and has no legislative fixation. It depends upon the company policy and usually will be the same for all irrespective of the employee's position, but some companies do also categorize the employees (like category I or category A). CCA is fixed according to the policy of the organisation and NOT calculated as percentage of basic pay. And two different companies may have two different amount of CCA in the same city. (And I suppose Allowance is paid no more as CCA since 2008 as per the amendment of pay commission in 2008. CCA is ABOLISHED. It might have covered under HRA/DA/SA, but it depends upon the company policy).
For more clarification refer : india.gov.in/govt/studies/allowances.pdf
usually HRA, is paid now not CCA, it is 40% in other cities and 50% in metros on your basic,
so if your basic pay is 20000 the HRA is 40% of 20000 , if you say 11000 (11000pm HRA not CCA then your basic pay may be around 27500/- pm) so make sure it is HRA paid to you and not CCA... CCA is just a variable pay to compensate to some extent and fully taxable unlike HRA, when CCA is abolished hence not considered while paying tax then how can any company pay it.......
it has to be HRA or DA, anyways, mail me the details......