This is due to rota infringement rules being applied at the forecast stage. If you turn off the rota infringement rule for salaried employees during the forecast submission, this will only check hours worked against the contracted hours when the rota actual submission takes place.
To turn this off, follow the below steps:
Go to Configuration and then click Settings.
Click System Settings and then select Rota Variables Rules.
Switch on the Only Run Rota Conflicts When Submitting Actuals.
📌Note: Switching this on will mean that the rota conflicts will only get checked when submitting a rota in an actual stage. The conflicts will not be checked when submitting a forecast rota.