Hello,
Sorry, but we don't understand your issue and you don't mention what phpdocx methods you are using. Are you adding the HTML content using embedHTML, WordFragments or replacing a template placeholder? How have you set the Arial font family and 6 as the font size?
Please post the most simple PHP code that illustrates your task using phpdocx standalone. To insert a sample code you can use the last icon of the WYSIWYG editor. Or you can send to contact[at]phpdocx.com this sample code.
Regards.