ffmpeg - Increasing file size after rendering

i used ffmpeg library for crop video in android project. user captur video with device camera

10-sec video original 640x480 = 200 KB

after crop by ffmpeg:

10-sec video Cropped 640*417 = 1.4 MB !!!

i used this cod:

-i video.mp4 -vf crop=640.0:417.10345:0:0 -threads 5 -preset ultrafast -strict -2 videocropped.mp4

Why then crop the file size is increased?!!!

pleas help me

--EDIT--

Details Camera Device for Original Video Capture:

Format File = mp4

video Encode Bitrate = 256000

Frame Rate = 30 frame per sec

video size = 640x480

video encoder = H263

audio encoder = AMR-NB