understanding economic open pit nickel grades, page-6

As I am relatively new to understanding how mining works , is there any references, books or website that is a good starting point ?

I'm still a bit baffled with the jargon that is being used.

Eg hole three from 45.m to what ? To the top of the surface or the bottom ? To how low ? Or is there a range in between. As you guys know more than I do , what is the best point of reference to understand how drilling / mining work. I don't expect anyone to spoon feed me anything but point me in the right direction will be much appreciated .

onceover, I cannot thank you enough for providing such insightful information. Once again thank u so much ^^

Let's hope our Assay would please the market !!