In the current code and when we are doing our work, we always assume that “from one source” means that it is coming from the same individual or the same legal entity, as civil law calls it. So the source is an individual. For example, four individuals from the same family may each give someone a gift. In that case, we look at the value of the gift given by each individual, and not the total of the amounts. That is explained by the fact that those individuals have a specific, defined and unique legal personality.
That is how the code is currently interpreted, and that is also the interpretation we recommend.