If you are having trouble with formatting, especially pasting from Word or any word processor, using the tinyMCE (the thing with the format buttons on), you will likely find a lot of mess and wrong sizing turning up.

The best way to avoid this is to press the little clipboard with the W on it (just under the font size dropdown) and paste your text in there. Then press insert. Once you do it that way, all the 'junk code' from the word processor is stripped and you can format your fonts normally to whatever sizes and style you like.

The other option is to uncheck the use tinyMCE box and paste your text directly into the box and format manually with code.