You wanted to know why the time confirmations shows more than 24 hours in a day.
SAP Business ByDesign
when time confirmations are to be written off , system combines the hours of many such time confirmations of an employee togerther and thus the total hours may go more than 24 hours.
Since the value will be zero for written off entries you can proceed with such project invoice request .
KBA , SRD-PRO-INV , Projects Customer Invoicing , Problem