Check this discussion on a 5x10(4) spore concentration:
Note the answer from: Susann Auer · - · Technische Universität Dresden:
"Since you obviously have to adjust your spores to an exact concentration I recommend that you count as many squares as possible and repeat your counting with another sample of your spore suspension. So you will assess proper mixing of the sample prior to counting.:
How to find the find the concentration of fungal spores? - ResearchGate. https://www.researchgate.net/post/How_to_find_the_find_the_concentration_of_fungal_spores2 [accessed Feb 7, 2017].