Why does ImageReader return incorrect BufferedImage?

I'm trying to access a animated GIF image with 21 frames and then read the 12th (cause it starts at 0?) frame.

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import javax.imageio.ImageIO;
import javax.imageio.ImageReader;

import org.apache.commons.io.FileUtils;
import org.apache.commons.io.filefilter.IOFileFilter;
import org.apache.commons.io.filefilter.SuffixFileFilter;
import org.apache.commons.io.filefilter.TrueFileFilter;

public class PictureSearch {

    public static void search(File file) {
        try {
            ImageReader reader = (ImageReader) ImageIO.getImageReadersBySuffix("gif").next();
            reader.setInput(ImageIO.createImageInputStream(file), false);
            BufferedImage caption = reader.read(12);

            System.out.println(caption.getHeight());
            System.out.println(caption.getWidth());

            caption.flush();

        } catch (IOException e) {
            System.out.println(e);
        }
    }

    public static void main(String[] args) throws IOException {
        List<String> suffixes = new ArrayList<String>();
        suffixes.add(".jpg");
        suffixes.add(".gif");
        suffixes.add(".bmp");
        suffixes.add(".png");

        Iterator<File> files = FileUtils.iterateFiles(new File(
                "F:/test/"), (IOFileFilter) new SuffixFileFilter(
                suffixes), TrueFileFilter.INSTANCE);

        while (files.hasNext()) {
            File file = (File) files.next();
            PictureSearch.search(file);
        }

    }
}

The reader should return me a buffered image with height 220 and width 200 (or height 205 and width 188 if it ignores white fields around the image). But what it does is it returns me a image of height 155 and width 174 what is absurd because i triple checked and the frame 12 is height 220 and width 200. Am I doing everything correctly in reading the frames?