Understanding CTC and HRA
CTC (Cost to Company) is essentially a term that HR created to give candidates and employees the impression that they are paid more than they actually receive. The term is not recognized in any labor law in India and is not defined anywhere. Therefore, you are free to choose what percentage you wish to have.
However, please check the income tax requirements on HRA as it will affect the amount of tax paid by the employee. Generally, people consider between 30% and 45% of Gross as HRA.