Trouble with font size

I have set the arabic font KacstOne to be default with font size 22pt by going to Tools->Options->LibreOffice Writer->Basic Fonts (CTL). However whenever I start writing using arabic font, the font will be KacstOne but the size will remain 12pt. If I change it manually to 22 it will change automatically to a bigger size which is 40pt in my case once I start typing. How do I fix this? The font size should automatically change to 22pt when I start typing arabic.