This is not something you can currently see before adding the web project to your web page. The best way to see the size of font data loaded by your web page is to (in Chrome) open dev tools, select "Disable cache," filter by "use.typekit.net," and load your page. This requires you add the web project to your page first, of course.
Note that your web page will only load the fonts that are actually used on your web page, even if you've added more fonts to your Web Project. Also, if your web project uses East Asian fonts, the fonts are delivered using "dynamic subsetting" to optimize your page load performance. More information about web fonts performance and subsetting here:
Hope this helps.