Question of deductibility of an expenditure u/s. 57(iii) of income tax act, 1961

I am pensioner and owner of flat in Coop. Housing Society in Pune and now building is demolished by builder/ developer for redevelopment. I am receiving Rs.20000/- p.m. rent compensation from Builder. Whether I should show it in other income under Sec 56 and claim deduction under Sec 57. Or should I claim only 30% of Rent received for deduction like HRA. Is HRA clause is applicable to pensioner in this case.I earned Rs20000/- as other income for expenses on rent notionally paid to son's flat occupied. In ITR there is provision about other income earned but no column for deductions under above section. Should I only report but not include in computation of Income