The Increment and DecrementFontSizeCommand change the font size of the current text in the editor by 2 points. At this point, the behavior of the two commands cannot be customized so that user-defined values could be used.
As for the HTML output, HtmlFormatProvider uses pixels as a measuring unit when exporting the font size of the spans. In order to convert points to pixels, the value is multiplied by 4/3, for example:
1 pt = 1.33 px
12 pt = 16 px
14 pt = 18.67 px
16 pt = 21.33 px
This is why the values do not appear as whole numbers.
On the other hand, in order to have the values 10,13,16,18,24,32 and 48 px in the exported HTML, the following values must be set to the spans in the document and visible in the UI of the editor:
10 px = 7.5 pt
13 px = 9.75 pt
16 px = 12 pt
18 px = 13.5 pt
and so on, which are not whole numbers again.
We have decided that it would be better to use whole numbers in the editor, as this creates a better user experience. Could you share some details as to why you would like to use the values you listed?
All the best,
the Telerik team