<span class="counter">100</span>
let counter = $('span.counter');
setInterval(function () {
let min = (Math.random() > 0.5) ? 0 : 5;
let max = (Math.random() > 0.5) ? 5 : 10;
let c = parseInt(counter.text());
let r = Math.floor(Math.random() * (max - min + 1)) + min;
if (Math.random() > 0.5) {
counter.text(c + r);
}
}, 2000);