It appears that you are capturing your monitor, so if OBS is running on your monitor then it will also capture that as well. I recommend adding a new source by right clicking under the "Monitor capture" tick box.
You will then be able to choose the source for your capture/stream. It will automatically detect your source if you have your game up and running. Once you have set up a new source you will also need to un-check "Monitor capture"
I am no expert as I have only started using OBS a few days ago so I may be wrong.....
