.countdown-wrap {
    width: 100%;
    max-width: 600px;
    margin: 20px auto;
    text-align: center;
    text-shadow: 0px 2px 2px rgba(0, 0, 0, 0.4);
}

.countdown-title {
    text-transform: uppercase;
    font-size: 20px;
    letter-spacing: 3px;
    font-weight: 400;
    padding: 0 30px;
}

.countdown {
    list-style: none;
    margin: 20px 0;
    padding: 0;
}

.time-wrap {
    display: inline-block;
    width: 25%;
    padding: 0;
}

.time {
    display: inline-block;
    font-size: 40px;
    font-weight: 700;
    letter-spacing: 0.05em;
    line-height: 1;
}

.unit {
    text-transform: uppercase;
    margin-bottom: 0;
    font-size: 14px;
    font-weight: 700;
    letter-spacing: 0.1em;
    line-height: 1.6;
    margin-top: 5px;
}

.countdown-wrap {
    width: 100%;
    max-width: 600px;
    margin: 20px auto;
    text-align: center;
    text-shadow: 0px 2px 2px rgba(0, 0, 0, 0.4);
}

.countdown-title {
    text-transform: uppercase;
    font-size: 20px;
    letter-spacing: 3px;
    font-weight: 400;
    padding: 0 30px;
}

.countdown {
    list-style: none;
    margin: 20px 0;
    padding: 0;
}

.time-wrap {
    display: inline-block;
    width: 25%;
    padding: 0;
}

.time {
    display: inline-block;
    font-size: 40px;
    font-weight: 700;
    letter-spacing: 0.05em;
    line-height: 1;
}

.unit {
    text-transform: uppercase;
    margin-bottom: 0;
    font-size: 14px;
    font-weight: 700;
    letter-spacing: 0.1em;
    line-height: 1.6;
    margin-top: 5px;
}

@media screen and (min-width: 768px) {
    .countdown-title {
        font-size: 28px;
    }
    .time {
        font-size: 54px;
    }
    .unit {
        font-size: 20px;
    }
}

Adjust font size on big screens
Adjust font size on big screens
