Need to amend form 4868. I had listed an amount under "Amount you're paying" even though at the time of extension request I did not pay anything. This skewed my return.

If you need to delete a payment,  see this Extension FAQ for how to get there.  Then you can change to amount to zero.

https://ttlc.intuit.com/community/tax-payments/help/how-do-i-get-credit-for-tax-payments-i-made-with-my-extension/00/26817

Ok ... if you aready successfully efiled or mailed in your return you have nothing that needs to be amended ... the IRS will catch this "math error" as they call it and recompute the bottom line.  If this means you will now owe they will send you a bill  or you can be pro active and send/make a payment now to reduce the penalties and interest.