Ann: Investor Presentation - Sibanye-Stillwater Investment, page-141

Sorry but what an irelevant calculation. I know that a DFS NPV is not an accurate measure of an asset's saleable value but nor is the book value on the annual report!
You've used a a valuation for the rhyolite ridge asset of $114m to show an increase in bv when you add a big chunk of cash to the JVco.
Plug any realistic value into your spreadsheet for the transfer of that asset to the JVco and the value to INR shareholders has gone backwards.
The JVco is not just getting a bare patch of land with some lithium in it and nothing else. They benefit from all the work done to date, all the offtakes, drilling, reports, buckwheat shenanigans etc. I.e. all the 'non book value' component that made up yesterday's $0.74 share price.
Take your pre JV bv of $0.1, which means the non bv component was $0.64/sh.
Your post JV bv is $0.269, now add back 50% of the non bv component or $0.32/sh and voila $0.59/sh which is pretty much bang on where we closed.
Not a value accretive deal for INR shareholders in terms of the recent share price. A pretty damn good deal for the JV partner though.
However most likely a necessary deal and it would have been locked and loaded when the SP was in the 60s so it just means it was getting a bit over bought.