Then I'm not sure I understand your question. Do you want to stretch/distort the 8x8 tilemap to fit perfectly into 428x240 viewport?
Or do you want to distort your entire game to fit into any monitor or window resolution? This may be a bad idea because there are ultra wide monitors with aspect ratios like 30:10
Also, seems like you don't understand the difference between Scale Inner and Scale Outer modes. Scale Inner cuts off parts of your layout, Scale Outer shows more of your layout.
construct.net/en/tutorials/supporting-multiple-screen-17