These counter are the easiest way to keep track and show people how far you are.
Now the way they work is, at the end of the url there is a number the number is 60 but of corce you wont have 60% the whole time so you change that number
Change it to 10 and it will show the image as 10%
Change it to 20 and it will show the image as 20%
Change it to 30 and it will show the image as 30% ect.

