Here's how to reproduce:
- Open image in XnView and go to Image / Adjust / Brightness/Contrast/Gamma/Balance Or just use (Shift+E)
- Change Gamma correction to any value
- Press the Previous or Default values button
- Now change Gamma correction with the small arrows next to Gamma box
What you shoud see is that Gamma correction level is changing by the the value before using the Previous or Default values button.
