The local office are trying to determine whether your wife can claim for you as a dependent or Qualified Adult. Even though she has declared that she is only claiming for herself, the local office must check in case there is an additional entitlement to a payment.
Information from Welfare.ie (earnings are weekly, gross before tax & PRSI deductions)
If your adult dependant is earning less than €100 you will get a full Increase for a Qualified Adult .
If your adult dependant is earning between €100 and €310 you will get a reduced-rate of IQA.
If your adult dependant is earning more than €310 you will not get an Increase for a Qualified Adult