8 Where a pensioner, contributing for elected augmenting service by way of repayment by instalments any amount required by section 6 or by way of making the deductions required by section 7, ceases to serve on augmenting service before payment of those instalments or deductions have been made in full, he shall be deemed to have contributed in respect of the augmenting service for which he elected and the remaining instalments or deductions shall be reserved out of his pension.