https://steamdb.info/app/346110/depots/

ArkWindowsSize.js

function ArkWindowsSize() {
    const units = ["B", "KiB", "MiB", "GiB", "TiB", "PiB", "EiB", "ZiB", "YiB"];

    function toBytes(sizeStr) {
        const [value, unit] = sizeStr.split(" ");
        return Number(value) * Math.pow(1024, units.indexOf(unit));
    }
    function fromBytes(bytes) {
        let unitIndex = 0;
        while (bytes >= 1024 && unitIndex < units.length - 1) {
            bytes /= 1024;
            unitIndex++;
        }
        return `${bytes.toFixed(2)} ${units[unitIndex]}`;
    }

    const totalBytes = [
        ...document.querySelectorAll("#depots table .octicon-windows"),
    ]
        .map((e) => e.closest("tr").querySelector("td:last-of-type"))
        .filter((e) => e.className === "")
        .map((e) => toBytes(e.innerText))
        .reduce((a, b) => a + b, 0);
    return fromBytes(totalBytes);
}
ArkWindowsSize();