These stats represent the percentage of searches which result in one or more clicks vs the percentage of searches that don’t lead to any clicks at all.
Let’s take a closer look at the keyword “chauffeur” as an example. Its search volume is 58K and its clicks count is 10K. One may be confused, because 10K doesn't make 20% of 58K.
The thing is, those clicks are not distributed within searches equally. 80% of the searches didn’t result in any clicks at all, while 20% of them resulted in some clicks (not necessarily one, it can be 2, 3 and more per search). When summed up, they will make 10K clicks in total.