I installed the latest version 3.4.25 and tried the following scenario

1- I added a stock product purchase price $ 33 and sale price $ 55 2 - I added a store leveling plus 10 pieces 3- I made a sales invoice number “SALE2019 / 10/0001” for one piece Sale price $ 55 and applied a discount of 1.5 and the total invoice $ 53.5 has been paid in full and the bill is complete 4 - I made a return for the same invoice was returned piece and return the amount of 53.5 dollars 5 - Experience on the points of sale. Experiment Result: When viewing the invoice list, reviewing the invoice “SALE2019 / 10/0001” and reviewing the return invoice, I find the wrong values. http://prntscr.com/pi1g34 http://prntscr.com/pi1gwk http://prntscr.com/pi1hau