Confused on baker's percentage

I have been perplexed by what I see as several inconsistencies in how people express baker's percentage in their sourdough formulas. Some seem to be saying the base for the percentage calculations of other ingredients should be the total weight of just the flour itself, others seem to be talking about the weight of the flour and water combined. I want to get this clarified since it is particularly important in how much salt I use. 

For example, if I am starting with 400 g. flour and using 2% salt, that would be 8 g. of salt. However, if we are using combined weight of flour and water (e.g. 75% htydration of same flour would total 700 g.) it woukld be 14 g. of salt -- big difference.

I'=m not looking for suggestions on how much salt to use; I'm lookikng for clarification of baker's percentage. 

Thanks.