Dear Sir,
Hope you are doing well !!
1. Where a resident makes a purchase of a property from an NRI, TDS is deducted at the rate of 20% (plus cess and surcharge, as applicable) if there are long-term capital gains; the rate is 30% (plus cess and surcharge, as applicable) in case of short-term capital gains.
So, IT department can't ask more than that.
2. There is no specific timeline mentioned in the income tax laws which states by when such mistakes must be rectified. However, it can take 30-45 days to reflect the same.
You can correct the same online.
We may assist you in entire procedure.