One problem about mygui's dll file

I have build mygui many times and try to change cmake's building entry every time
every time I compile it
dll lib's size must be 50MB much more
but the MYGUI_3.2.0_win32 zip file which I download from http://mygui.info/
has an MyGUIEngine.dll which just 1.71MB
why? 50MB vs 1.71MB ~~!!It may be a large gap, right?
please help me
(my os is xp.sp3,and I using mingw32 to compile the lib)

I guess you have debug version with all debug related data inside.

thanks for reply
it's looks really what you say
I do not to change the cmake building entry
so the default building is RelWithDebInfo