Ann: More Thick Zones of Spodumene-Bearing Pegmatite at Seymour, page-30

Can't say I'm an expert myself but think through what you are proposing:

When the lithium bearing spodumene is in the ground the average grade might be around 1.5%. To refine that to 6% (4x the concentration) you essentially have to take 4t of material that you've dug up, then remove 3/4 of the non-lithium bearing component so the ~1t of remaining material has all the lithium oxide bearing part in it.

I.e. For 20Mt at 6% concentration you need to dig up 80Mt at 1.5%.

ADV has an initial target of 5Mt JORC resource, so you are assuming a resource that will be 16 times what they are trying to achieve in the near to medium term.

As I said I'm no expert but this seems wildly unlikely, to put it mildly. More than happy to be wrong but if you are expecting a $16b company you will probably be disappointed mate