Workweek Countdown

I really like this extension. Works perfectly for me and gives me motivation while working as I'm the type of person who trudges on by telling myself 'Just one more day etc' .. But I'm sad that this countdown doesn't have a dark theme as white numbers with a white background is not so aesthetically pleasing..

After adding this extension, it does not work as those images are shown. When a user (assuming a Windows PC) clicks on the extension, it just opens up a new tab directing the user to this same window/website, NOT the countdown timer. Please fix! Update: it works but not sure what or how I did it. After starting the count down, I cannot edit the "time schedule". Help?