Hello. I noticed that you are using an editor to enter textarea fields. When you use the editor, it gives precedence to the settings that were entered through the editor. In this case, we see the following font information in the editor: size 12pt.
And it is this size is displayed on the site, as it is specified in the HTML markup lower than the size you set in the field settings. So to change the size, you need to change it in the editor.