Basic and Advanced grade & potency coexistence 25 and 08

Dearl all,

Three questions related to this preference

1- What's the purpose of the sequence n° in this preference. We're using both data (Grade values range & days before). As both are returned values (in blue) , I can't understand the logic when the preference is resolved for customer/item , I suppose only first sequence is read?

2- Is the preference resolution (F40300R) managed in case of ADVANCED preference? (as there is no R40400).

3- We faced an issue whenever we activate both 25 and 08. Unlike the documentation is stating, if there is no preference found in 25, the basic 08 didn't used. We're compelled to choose one of them by removing advanced Grade schedule in order to let the 08's working....