Can't find source of data Firefly uses to create quantitative images

using firelfly to produce index maps of frequency data but can’t find source of data that Firefly uses to produce these maps. (I found that the images Firefly produced were beautiful but when carefully checked the data seemed to be completely made up. That is, it seems that Firefly -like most AI bots - hallucinates - but it would be nice to be able to check this against its source data).