The phrase "different mutations" refers to changes or variations in genes or DNA. It means that there are different types or versions of these genetic changes that can occur in living organisms. Full definition
As cells age, thousands of different mutations in each mitochondrial genome are possible. (sciencedaily.com)
They also found that structural mutations sometimes occur in tight clusters where a combination of different mutations occur all at once. (sciencedaily.com)
You can identify how many different mutations occurred, but not always how. (discovermagazine.com)