About GSTR1

Dear friends,

I am small business holder and availed quterly filling of GSTR1 .....During the sep 2017 I filled GSTR-1 For Q2 but by mistake I did not mention Sales data of Auguest month therefore Gst turnover is showing less amount by 3,20,000 and now I want to file Income tax and there need to GST turnover.

1.so which GST turnover show in Income tax portal.
2. how to mention this Aug month sales data in GST portal.

Plz suggest me.