I have two spark generators connected next to each other. Had about 100 peaty soil laying around that I split into two stacks of 50. When I put the first stack of 50 in on the left slot in the spark generator, it read 2.9 spark/s. Then, I put the second stack of 50 in on the right slot and it reads 5.7 spark/s.
= 5.8 spark/s
Not that the .1 difference is all that big, but could just be a typo error.