You have refunded more tax and USC to employees in one period than the tax and USC deducted from all employees.
On your P30 return, you must enter an amount of 'Nil' in the PAYE and USC fields. You must enter the full amount of PRSI deducted from your employees' wages and your employer share.
Your refund of tax and USC can be deducted from the tax and USC due on the next payday, or you may request a refund from the Collector General.