Comma separated list of style values that is to be used when the user selects font sizes, this option is only used when the convert_fonts_to_spans option is enabled. This list of style values should be 7 items. This option is not used by default, but can be useful if you want to have custom CSS values for each font size for browser compatiblity. Defaults to: xx-small,x-small,small,medium,large,x-large,xx-large.
Example of usage of the font_size_style_values option:
tinyMCE.init({
...
font_size_style_values : "xx-small,x-small,small,medium,large,x-large,xx-large"
});