Am I actually using the BigQuery slots I am paying for?

-- Baseline paid for against the slots this project's jobs used, by hour.
-- RESERVATIONS_TIMELINE has a row for every minute a reservation exists, so
-- idle hours count, as they are billed. It lists the reservations of the
-- project this runs in: run it in the reservation administration project,
-- or put that project's ID in front of the view name.
WITH capacity AS (
  SELECT
    reservation_id,
    TIMESTAMP_TRUNC(period_start, HOUR)                      AS hour,
    AVG(slots_assigned)                                      AS baseline_slots,
    SUM(period_autoscale_slot_seconds) / 3600                AS autoscale_slots
  FROM `region-us`.INFORMATION_SCHEMA.RESERVATIONS_TIMELINE
  WHERE period_start >= TIMESTAMP_SUB(CURRENT_TIMESTAMP(), INTERVAL 14 DAY)
  GROUP BY reservation_id, hour
),
usage AS (
  -- Script parents repeat their children's slot use; job_creation_time is
  -- the partition column, so it is what limits the read.
  SELECT
    reservation_id,
    TIMESTAMP_TRUNC(period_start, HOUR)                      AS hour,
    SUM(period_slot_ms) / 3600000                            AS slots_used
  FROM `region-us`.INFORMATION_SCHEMA.JOBS_TIMELINE_BY_PROJECT
  WHERE period_start >= TIMESTAMP_SUB(CURRENT_TIMESTAMP(), INTERVAL 14 DAY)
    AND job_creation_time >= TIMESTAMP_SUB(CURRENT_TIMESTAMP(), INTERVAL 15 DAY)
    AND reservation_id IS NOT NULL
    AND (statement_type != 'SCRIPT' OR statement_type IS NULL)
  GROUP BY reservation_id, hour
),
hourly AS (
  SELECT
    c.reservation_id, c.hour, c.baseline_slots, c.autoscale_slots,
    IFNULL(u.slots_used, 0)                                  AS slots_used
  FROM capacity c
  LEFT JOIN usage u USING (reservation_id, hour)
)
SELECT
  reservation_id,
  COUNT(*)                                                    AS hours,
  ROUND(AVG(baseline_slots), 0)                               AS baseline_slots,
  ROUND(AVG(slots_used), 1)                                   AS mean_slots_used,
  ROUND(AVG(autoscale_slots), 1)                              AS mean_autoscale_slots,
  ROUND(COUNTIF(slots_used < baseline_slots) / COUNT(*), 3)   AS share_of_hours_below_baseline,
  -- Use is at or above these levels in 80% and in 60% of hours.
  ROUND(APPROX_QUANTILES(slots_used, 100)[OFFSET(20)], 1)     AS slots_used_in_80pct_of_hours,
  ROUND(APPROX_QUANTILES(slots_used, 100)[OFFSET(40)], 1)     AS slots_used_in_60pct_of_hours,
  ROUND(APPROX_QUANTILES(slots_used, 100)[OFFSET(95)], 1)     AS p95_slots_used
FROM hourly
GROUP BY reservation_id
ORDER BY mean_slots_used DESC;