Why won't my script resize the font to size 13?

I have JavaScript code that is supposed to change the font size for all text boxes. I want to resize the font to size 13. The text boxes range from size 4.76 to size 10.49. Right now, the script only changes them to size 12 or 14 (or anything that isn't 13).

var myDocument = app.activeDocument;  
  
  
var tfs = myDocument.textFrames;  
var n = tfs.length;  
  
  
for ( i = 0 ; i < n ; i++ ) {  
          tfs.textRange.characterAttributes.textFont = app.textFonts.getByName("BebasNeue");   
          tfs.textRange.characterAttributes.size = 13; //nothing happens during this stage unless I change 13 to 14  
}  

Thanks in advance for any help.