'Set Number Of Processors' working?

Hey! The 'Set Number of Processors' option doesn't seem to remember my settings. Everytime I open it, it displays 2 as the value, whereas the number of available logical processors is higher. I've read in the forums, that the performance would actually get worse, if it is set to a number higher that 2, but this was in 2011 I think, so I was wondering, if the multithreading is working or not? If yes, the option dialog doesn't remember my information.

Currently it seems set to 2 can increase the performance a little bit, but it gets worse if it's set to more than 2. My computer only has two cores so I have stoped the threading development and just cap it to 2.