Amendments to Registration

I have query regarding amendments in Registration.Actually at the time of migration some info regarding reg was incorrect which I was noticed now itself.so my doubt is when I opted to amend the details in Gst website it is asking regarding the effective date of amendment.As the amendment is of info existed during migration itself I opted the date as 1.7.17.But as per the provisions of Gst the amendments in Registration as to be informed within 15 days from date of change.so my doubt is whether I can select the date as 1.7.17 or 15 days prior to date of opting.so please resolve my issue and let me know the solution.