What that is showing you is that your model is about 1 ft tall. The checkered image there is the size of a normal character in Game Guru.
You will have to scale your model up, then choose Tools/Bounding Box/ Save bounding box.
Save the milkshape project file, then.
Re export your model and try it again in Game Guru.
http://www.wings3d.com/?page_id=923Intel(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.