There is no way to correct the existing timesheet once posted, however it is possible to effectively reverse out the transaction. To do this:
Log in to FocalPoint Admin.
Click System Options, Time Recording, Timesheet Entry
Select the allow negative hours on timesheets checkbox.
Log in to FocalPoint web.
Click Timesheets.
Enter a timesheet for the same project, cost centre, user and day with the same hours but negative — for example, if the incorrect timesheet is for three hours, enter -3.
Post this negative timesheet. The negative timesheet will cancel out the values against the accounts and negate the effect of the incorrect timesheet allowing you to post a correct one.
In FocalPoint enter a timesheet with the correct details.