How to Export Files from Adobe Illustrator
If you use Adobe Illustrator to create your image files, but don't export your files correctly, you may find that your images are not sized correctly. Please use the following process:
You can export your image by clicking:
File > Export
File Save for Web
You may also need to verify that you are exporting based on an artboard that is the correct size.
If saving with the correct artboard size and format does not solve the problem, you may be experiencing a known bug Adobe is working on. The current fix is to save the file as CS6 (problem is in the new updates to CC). Saving it as a CS6 is supposed to make it save correctly. You can find this information in the top post here https://forums.adobe.com/thread/825904?start=40&tstart=0
Essentially, you may need to roll back your version of Illustrator to an earlier version: http://blogs.adobe.com/adobecare/2015/06/16/how-to-find-and-install-previous-version-of-adobe-apps-in-cc-2015/