Riva flv encoder problem

Im using riva flv encoder on a video-file and i have noticed something that isnt right.
I have output the video in two different formats (320x240 and 480x360) but the two files are nearly the same size (39mb) - all the other settings are exactly the same, so isnt the bigger format file supposed to be at least two times the size of the small file? And if so, can anyone help me get it right.