penalty for NRI having purchase flat from resident account.

Hi! I'm an NRI living in Moscow since 2013. In India, I hold NRE, NRO n resident savings account. in Jan 2015 purchased a flat and deposited cash around 15Lacs n issued a DD for registration of flat from my resident savings account(Without knowing it's not a legal process). This 15Lacs have transferred from Moscow to India during 2013 n 2014 into my NRE account. I haven't filed ITR since 2013 as am not liable to pay tax n will close my savings account as soon I visit India. In Nov 2017, got a notice from IT... AIR-001 Deposited Cash of Rs. 10,00,000 or more in a Saving Bank Account EXC-001 Cash transactions exceeding Rs. 10,00,000/- in a month TDS-195 TDS Return - Other sums (Section 195) and responded the above as... Self-Investment/expenditure is out of accumulated savings Self-Income from transaction is exempt I would like to know from you about the further general, in how much time the IT people will reply to my response and what other docs or proof can they demand...n what penalty for an NRI having purchase flat from the resident account? on Internet, its written...under Section 13 of The Foreign Exchange Management Act, its 3 times where such amount is quantifiable, or up to two lakh rupees where the amount is not quantifiable... it's not clear to me, in my case the amount is quantifiable? Please help me out. Thank you!