I have wrongly selected an input for quantity adjustment and resulted to negative cost. How to correct it in Sales and Profit and Loss Statement.

Welcome to the Community, @rudney_rmd.

You're referring to inventory quantity adjustment, correct? If so, you can edit that adjustment to correct the quantity instead of doing it in the Sales and Profit and Loss Statement.

The steps to do it are pretty quick and easy. Here's how:

1. In QuickBooks Online (QBO), tick the Search icon at the top right. 
2. Select Advanced Search, then pick Inventory Quantity Adjustment in the All Transactions drop-down.
3. Hit Search and locate the adjustment to edit.
4. Enter the correct quantity and click Save.

For more information about the process, refer to this article: Adjust inventory quantity on hand in QuickBooks Online. After that, run the Profit and Loss report again to double-check.

Please let me know if you're referring to something else or if you have any other concerns. I'm always here to assist. Have a good one!