The solution in itself was correct, but some errors were probably caused by the multiple break-conditions that you have set up inside of the for-loop, such as:

        if (days <= 0) {
            break;
        }

OR

        if (totalEatenFoot >= totalFoot) {
            break;
        }

Keep your code as simple as possible to allow for faster analysis when submitting exercises during the exam, having a separate dayCount is not necessary when you can use i from the for-loop. Also, calculate the final food amount once the loop has been terminated, since it is not needed to calculate it anew with each loop iteration.

Best,

Code:

function footFotPets(input) {
    let days = Number(input[0]);
    let totalFoot = Number(input[1]);
    let sumDogFoot = 0;
    let sumCatFoot = 0;
    let totalEatenFoot = 0;
    let totalPercent = 0;
    let sumBisscuits = 0;
    let totalDogPercents = 0;
    let totalCatPercents = 0;
    // let dayCount = 0;
    let counter = 2;

    // for (let i = 2; i < input.length; i++) {
    for (let i = 1; i <= days; i++) {

        // if (days <= 0) {
        //     break;
        // }

        let dogFoot = Number(input[counter++]);
        let catFoot = Number(input[counter++]);
        // dayCount++;

        sumDogFoot += dogFoot;
        sumCatFoot += catFoot;
        // totalEatenFoot = sumDogFoot + sumCatFoot;

        // if (totalEatenFoot >= totalFoot) {
        //     break;
        // }

        // if (dayCount % 3 == 0) {
        if (i % 3 == 0) {
            let currentSumBisscuits = (dogFoot + catFoot) * 0.10;
            sumBisscuits += currentSumBisscuits;
        }


        // if (dayCount >= days) {
        //     break;
        // }
    }

    totalEatenFoot = sumDogFoot + sumCatFoot;
    totalDogPercents = (sumDogFoot / totalEatenFoot) * 100;
    totalCatPercents = (sumCatFoot / totalEatenFoot) * 100;
    totalPercent = (totalEatenFoot / totalFoot) * 100;

    console.log(`Total eaten biscuits: ${Math.round(sumBisscuits)}gr.`);
    console.log(`${totalPercent.toFixed(2)}% of the food has been eaten.`);
    console.log(`${totalDogPercents.toFixed(2)}% eaten from the dog.`);
    console.log(`${totalCatPercents.toFixed(2)}% eaten from the cat.`);
}