How Does Rxjs Reduce In Case There Is No Matching Accumulator?

I was going through an article on Reactive Programming in JavaScript and not sure how the following example listed in there results in output 27 import {Observable} from 'rxjs-es';

Solution 1:

I have translated it to RxJs 6 and it doesn't output 27

const { interval } = rxjs;
const { map, filter, reduce, take } = rxjs.operators;

let output = interval(500).pipe(
 map(i => [1,2,3,4,5,6][i]), // very strange way of adding one to the intervaltake(6) // had to add a take so observable would complete else reduce would never emit
);

let result = output.pipe(
  map(num1 => num1), // Does nothingfilter(num1 => num1 > 4), // filters out those less than 5reduce((num1, num2) => num1 + num2) // add the leftovers 5 and 6
);

result.subscribe(number =>console.log(number)); // 11 is the output

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