An error occurs. "During the index, the field weight is worthwhile if each document is set"

Http://wiki.apache.org/lucene-java/LuceneFAQ#What_is_the_difference_between_field_.28or_document.29_boosting_and_query_boosting.3F

I want to find a formula to calculate the weight. When I look for it, I have no intention of finding the phrase "it is worthwhile to set the weight of the field during the index if every document is set". I didn't pay attention to it at first, however, the link to the original text is provided next to it. The original text is as follows:
Index time field boosts are worthless if you set them on every document.
It makes no sense to set the field weight for each document during index creation. I think it makes no sense to set the same weight,
However, it seems that "it is worthwhile to set the field weight in each document during the index period" is not appropriate,
Go to another web page and see the same words...