Your District will, at its own expense, make tests and inspections as required on its meters to insure a high standard of accuracy. Your District will, at its own expense, make a meter test upon customer's request provided that such meter has not been tested during the preceding four year period. Additional tests at request of customer will be made; and if a meter is found to register within two percent plus or minus, the customer shall pay a test fee of twenty-five dollars ($25.00). If the meter is found to exceed the two percent limit plus or minus, the bill may be adjusted accordingly for the preceding six month period and no charge will be made for the testing.