Hi Terry,
For this, you have to edit other js file: clockt.js.
This file is the "code" file, you will find on line #169
am.style.fontSize = (this.font_size * 2 / 3) + 'px';
...and on line #180:
zn.style.fontSize = (this.font_size * 2 / 3) + 'px';
change the parameter in red, this is the size 'Formula"
Regards,
Jacques