Math.random starts to generate negatives while shouldn't

I have an issue with Math.random(); I've made an AI for game "Guessing number game" and it works just fine until the Player hit number lower than searched number. After that Math.random(); may and it is very likely to generate negative numbers. If player hit the number lower than searched number. (Range of numbers gessing by AI is defined by two nums (the highest from array of nums lower[]; than searched and lowest from array higher[]; than searched). Here is whole code on GitHub since its too large to put it in here and i really don't know where issue can be located: http://ift.tt/2sgGrtX

Function starts to generate negatvies during executting this part of code:

else if(higher_l > 0 && lower_l > 0)
    { //losuje od 0 (ZERA) do (max-min+1) i dodaje + min;
        guessed = Math.floor(Math.random()*((higher[0])-((lower[0]+1)+1))+(lower[0]+1));

        if(guessed > drawn)
        {
            c2--;
            document.getElementById("notes2").innerHTML = p2 + " remaining chances: " + c2;
            higher.push(guessed);
            higher_l = higher.length;
            higher.sort(function(a, b) {return a-b;});
            resultH = resultH + guessed + " ";
            document.getElementById("higher").innerHTML = "Proper number is lower than: " + resultH;

            counter = setTimeout(checkCounters, 100);

            switch_trigger = setTimeout(switchPlayers, 2000);

            return;
        }
        else if(guessed < drawn)
        {   
            c2--;
            document.getElementById("notes2").innerHTML = p2 + " remaining chances: " + c2;
            lower.push(guessed);
            lower_l = lower.length;
            lower.sort(function(a, b) {return b-a});
            resultL = resultL + guessed+ " ";
            document.getElementById("lower").innerHTML = "Proper number is higher than: " + resultL;

            counter = setTimeout(checkCounters, 100);

            switch_trigger = setTimeout(switchPlayers, 2000);

            return;
        }
        else if(guessed == drawn)
        {
            p2w++;
            document.getElementById("all_wins").innerHTML = p1 + " wins: " + p1w + "/" + wins + "<br/>" + p2 + " wins " + p2w + "/" + wins;

            if(p2w < wins)
            {
                document.getElementById("msg").innerHTML = "AI found the number: " + guessed + "first!<br/>" + currentp + " and gets a point!";
                document.getElementById("next").disabled = false;
            }
            else if(p2w == wins)
            {
                alert("Winner is " + currentp + "!");
                document.getElementById("msg").innerHTML = "AI found the number: " + guessed + " <br/> Player: " + currentp + " reached required number of: " + wins + " wins first!";
            }

            end = setTimeout(endMatch, 100);

            return;
        }
    }

I know that the code itself could be a way better than this but i want to improve it when the whole thing will be working. I'll be very greatful for any help.

Regards