The default world coordinate system has 0,0 as the top left corner, and 100,100 as the bottom right hand corner of the screen (this can be changed using TAgkApplication.SetVirtualResolution). 

This method always positions the sprite using its top left corner, regardless of the current sprite offset. The top left corner used to position the sprite does not rotate with the sprite, for example as the sprite rotates around its center the imaginary top left corner remains fixed and the sprite's position value does not change.

SetPosition Method