In the third case, you can have a combination of manual and automatic model selection: you specify a model and set the system so that it additionally checks historical values for a seasonal pattern or trend.

Possible combinations that you can choose are as follows:

1. You enter a trend model for the forecast model and then let the system check historical data for a seasonal pattern by setting the model selection to seasonal for the test.
2. You enter a seasonal model for the forecast model and then let the system check historical data for a trend by setting the model selection to trend for the test.