public static int packingOutputBytes(int valCount, int bitWidth) {
        if (valCount == 0 || bitWidth == 0) {
            return 0;
        } else {
            // We pack 8 values a time.
            return ((valCount + 7) >>> 3) * bitWidth;
        }
    }
The number of bytes after packed those item with the bitWidth.
indexr-vlt-segment/src/main/java/io/indexr/vlt/codec/pack/PackingUtil.java