At the battle of Thermopylae, I don't believe there was a precise count of Persians involved. One reason I say this is because there were four different people who offered different versions about what happened during the battle of Thermopylae and what they claimed to be accurate. For example, four historians claim to have been this many Persian soldiers at the battle, and they claim to have used facts or sources that were either false or true. The historical evidence i´m using to proven my argument is that there were different varieties of authors who wrote these articles of what they thought was true or not for example Herodotus was an ancient greek historian, Ctesias was a greek physician and historian, Bradford was an english historian specializing in the ancient mediterranean world and Matthews who was an english author and a politician. I think this only tells me that since they all were from different time periods, one by one their evidence would only matter when they had published it or when it was told during their time.