The button in this section resets the big clock appearence to its default.
The defaults are:
enabled: yes
text color: black
text size: 10
text font: serif
clock color: red
clock size: 100
clock font: serif
indicator color: (same as clock color)
indicator font: serif
border color: gray
border size: 15
border style: solid
background color: mint
background transparent: no
padding: 20
autosizex: 100% of window
autosizey: 100% of visible window
i18n for big clock time: no
fullscreen position: biggest fit
moon phase: on
seconds display: on
event reminder: on
look here for more information on these settings.