How can i deal with UE render window's black edge?

Hi, I had post this message to forum, how can i deal with UE render window's black edge? - C++ - Unreal Engine Forums, but the support tell me to post here, please help, thankyou.

You can disable this behavior by typing this into the console: r.BlackBorders 0. Or you put r.BlackBorders=0 into consolevariables.ini

Thank You

Eric Ketchum