Yes, that is correct, change the graphics for all the sizes there.
Game Guru checks the users screen resolution and adjusts itself to that. So having all the resolutions customized is your best bet.
Make your largest ones first, then scale them down to the other sizes.
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz, 2400 Mhz, 4 Core(s), 4 Logical Processor(s), 8gb RAM, Nvidia gtx660, Windows 7 Pro 64bit, Screen resolution 1680 x 1050.