Great explanation @peachfuzz 
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@Mr.Chrontini, you are not in the same boat as Chow. Your soil is more acidic than Chow. Chow as a nearly perfect pH soil now. peachfuzz give a great answer, you even can have some bugs in a batch of soil and, from the same compagny but from another batch, you won’t.
As for my sources, the chart come from here ILGM forum, there is a topic called charts and graphs, you should take a look, it’s very informative 
Charts and graphs, and from my numburous years of gardening and study.
Hoping that’s gone a help you,
~Al 