Understanding Graphite

Hi All, I invested in RNU based on its (seemingly) potential for an offtake agreement. So essentially, I am speculating with RNU.

However, I was going over one of the presentations and felt like I needed to understand a few simple concepts to understand the true potential of RNU, so please be patient with me.

When the company claims:

"Mineral Resource: 80.6 Mt at 7.9% TGC for 6.4 Mt of contained graphite
Ore Reserve: 45.2 Mt at 7.9% TGC for 3.6 Mt of contained graphite"

Does this mean it only has 10 Mt of graphite? (6.4+3.6)
What is the 7.9% of total Mt it state mean?

I have some followup questions but would hope someone can explain this to me. I want to understand true profits RNU can look forward to based on reserves it has.

Thanks in advance.