But now when starting the server, I get a ValueError: The price_decimal 6 in [product] configuration section is different from the value 4 in 'ir.configuration'.
Running the trytond-admin command does not help either.
It is not recomended to update this settings after creating the database, as this may produce some data loss (specially if you reduce the number of digits).
For that reason, we store in the ir.configuration model the number of digits the database was initialized with. You can update them manually on the database at your own risk. Once the value of the database matches the value from the configuration the error won’t be raised anymore.