Making a GIF from a Video
In the "gif settings" box there's a value for "frame delay" which defaults at 100. This is the time in milliseconds between each frame.  The small it is, the faster the gif will animate.  

Frame delay of 100 is 10 frames per second.  If you have 30 frames per second, use 33 as the frame delay.  If you have 15 frames per second, use 67 as the frame delay.

Or just change the "frame delay" value until it looks right - smaller for faster speed, bigger for slower speed.

There's a pretty good overview of how to use the app in this article:

http://www.macworld.com/article/1164864/how_to_create_an_animated_gif_from_a_video_clip.html

Also note that the preview inside the app is limited to 10 frames per second or slower - if it looks slow inside the app, test it out in a real browser.