Spin-up period of OpenFlows FLOOD modelling

Hello, I have a question about OpenFlows Flood modelling. If I run a coastal modelling using OpenFlows Flood with this scenario:

1. The atmospheric parameters and tide as input

2. Set the salinity and temperature as constant value

3. The simulation duration is 30-31 days

How many days should the spin-up period be?  Is it automatic or where can I define the spin-up period?

Thank you in advance