The formatting of the string is controlled in a similar fashion as it would be in Microsoft Excel. In Excel, the user must select a portion of the text and set the various formatting properties of that selected text.
With the FormattedStringFont.formattedString, a portion of the string is "selected" by calling either GetFont(int) or GetFont(int,int). Formatting properties are then set on the returned FormattedStringFont and all characters in the font's selection range are given these properties.
Getting the formatting properties of a FormattedStringFont will return the formatting of the first character in font's selection range. This is similar to Excel, which will update the formatting interface to reflect the formatting of the first character in a selection range when a cell's text is selected.