It looks like the screenshot from your colleague may be using a different raster or layer, and they also have different values set in the Advanced symbol options for the Magnitude and Unit.
If you use the same data, and the same settings that your colleague is using, does the OK button appear?
Allo Kory, It's the same data but when I type enter because I don't have an OK button, it returns to the original value. Thanks for your quick reply
Marc