When an employee is auto enrolled, you cannot apply any override amounts (either Employee or Employer contributions) during the first payment period. Overrides can only be applied starting from the second enrollment period.
If this results in an underpayment of employer contributions, apply an override for the correct amount along with the underpayment amount during one adjustment period in the next payroll cycle. In the following period, you can then make adjustments to reflect the correct total and the remaining amounts for the adjustment periods.