In the first map (temperature), the area of each circle shows the magnitude of the standardized anomaly, which is calculated as (July mean - 1981-2010 mean)/(1981-2010 standard deviation). The second map (precipitation) depicts the significance of the precipitation anomaly by using the rank of the July total compared to the 30 July totals in the 1981-2010 period; so the largest possible circle is obtained when the July total is either smaller or larger than any in the 30-year period. If the July total falls in the middle of the historical distribution, the circle has zero radius (i.e. precipitation was close to average).
The numbers at the observing locations show the actual values for the mean temperature and total precipitation.