Can't adjust which array Item to look at inside a for loop

Hi there. I’m trying to compare items in two lists, but I want to compare the locations of two vehicles around the same time of day. So below is the code snippet. You’ll see the console log called TESTER WL, that prints the 4th (5th) item in the wheelLoader array correctly. Now in the for loop I want to compare items in the lists but in dumpTrucks I want the i’th item and in wheelLoaders I want the (i + 4)th item. But i + 4 inside the square brackets, in fact entering any number into the square brackets has no affect on the output. The output is always the items from the beginning to the end starting from the first entry. How do I get the (i + 4)th entry? Thanks very much

console.log("TESTER WL: " + JSON.stringify(this.wheelLoader1PosTodayMap[0 + 4].position) + " : " + this.wheelLoader1PosTodayMap[4].time);
      for ( let i = 0; i < comparisonNum; i ++ ) {
        console.log("WL: " + JSON.stringify(this.wheelLoader1PosTodayMap[i + 4].position) + " : " + this.wheelLoader1PosTodayMap[i].time);
        console.log("RD: " + JSON.stringify(this.dumptrucks1PosTodayMap[i].position) + " : " + this.dumptrucks1PosTodayMap[i].time);
      }