If a petition for reassessment is filed within 15 days, the department shall reconsider the assessment and, if the licensee has so requested in his petition, shall grant the licensee an oral hearing and give the licensee 10 days’ notice of the time and place of hearing. The department may continue the hearing from time to time as may be necessary. The department may decrease or increase the amount of the assessment. The amount of the assessment may be increased, however, only if a claim for the increase is asserted by the department at or before the hearing.