Giang,
Sorry for the delay. The configuration page you showed is for our automatic addition of the comments box to Joomla articles. Since you added the tag manually, you'll need to set the size you want to use in the tag. To do so, update the tag like below:
For the raw {JFBCComments} tag showing, that's an issue with whatever is calling the popup. When it's pulling the content from Joomla, it's not firing off our JFBCSystem plugin, which is used to replace the {JFBCxyz} tags with the appropriate Facebook calls. You'll need to make the content that appears follow Joomla standards and run the system plugins on it. The developer of the extension you're using should be able to help you with that.
Otherwise, you can replace the {JFBCComments} tag with the raw Facebook code. However, then you'll need to do some work to determine the proper URL for to use in the code, something that JFBConnect does automatically.
Hope that helps,
Alex