code: private String parseMaxAgeMplus(String value, long lastModified) {
          long currentTimeMillis = System.currentTimeMillis();
          return Long.toString(Long.parseLong(value) + (lastModified - currentTimeMillis) / 1000);
      }
docs: Parse value for a max-age (m + N value), according to the requested file's last modified date
  @param value
  @param lastModified
  @return max-age parsed value