I assume that the total number of occurrences is never the same otherwise you could choose the occurrence number directly on the variable extractor panel right?

Otherwise there's a simple way to achieve that goal. Each time you extract all occurrences there's a default variable created by NeoLoad. For instance, if your variable extractor name is "MyTest" then you will have ${MyTest_matchNr} that will contain the total number of occurrences.

So let's say you have an array of 5 values then this variable will contain 5. Now if you would like to get your highest value you can simply use this concatenated variable:

${MyTest_${MyTest_matchNr}}. In my example, this variable will be evaluated like this:

${MyTest_5} which should be the 5th occurrence and the last one.