Regarding gstr 3b filing

okay bhai. So I have mentioned total outward taxable supply along with total SGCT, CGST and IGST tax in 3.1 and separately mentioned nil rated supply there was well.

In 3.2 I have mentioned total sales for each state (taxable and nil rated) along with IGST amount for that state. Did i got that right?

Divakar Bhai, 

In GSTR 1, where should I input my taxable supply made through e-commerce portals? Is Tab 7, B2C Others the correct section?

Divakar Bhai, I made a mistake while filing GSTR 3B for July 2018. I mistyped the GST tax payable and therefore ended up paying Rs 20 less Integrated tax. I just realised it while filing GSTR 1 for the quarter. How can I rectify this mistake now. Is it possible to fix and pay remaining tax? And what penalty would I have to pay?

Divakar Bhai, I already filed this month's GSTR 3B. I noticed the mistake while filing quarterly GSTR 1. Pata nahi kaise itni badi gadbad ho gayi mujhse. I didn't realize that I mistyped the amount.

Divakar Bhai, any idea what should I do now??