code: private static long calculateTolerableVadility(Date thisUpdate, Date nextUpdate)
    {
      return maxLong((long) ((float) (nextUpdate.getTime() - thisUpdate.getTime()) *
                             TOLERABLE_VALIDITY_RANGE_RATIO), MIN_CACHE_WARMUP_TIME_IN_MILLISECONDS);
    }
docs: Calculates the tolerable validity time beyond the next update.
  <p>
  Sometimes CA's OCSP response update is delayed beyond the clock skew
  as the update is not populated to all OCSP servers for certain period.
  
  @param thisUpdate the last update
  @param nextUpdate the next update
  @return the tolerable validity beyond the next update.