Справка Collabora Office 22.05
Returns the number of samples in period as calculated by Calc in case of FORECAST.ETS functions when argument period_length equals 1.
The same result is returned with FORECAST.ETS.STAT functions when argument stat_type equals 9 (and period_length equals 1).
FORECAST.ETS.SEASONALITY (values, timeline, [data_completion], [aggregation])
=ПРЕДСКАЗ.ETS.СЕЗОННОСТЬ(Значения;Время;ИСТИНА();1)
Returns 6, the number of samples in period based on Values and Timeline named ranges above, no missing data, and AVERAGE as aggregation.