JabRef 3.6dev--snapshot--2016-08-22--master--74afbb7
windows 10 10.0 amd64
Java 1.8.0_101

Steps to reproduce:

1. Change Preferences > Appearance > Set table font to font size 14
2. Export preferences (xml)
3. Change Preferences > Appearance > Set table font to font size 10
4. Import preferences (xml)
5. fontsize is still 10 (should be 14)

Remark:
font size is saved in xml:
<entry key="fontSize" value="14"/>