This deal is
extremely weird; in the 4 decades I've been playing this game in one way or another I've never heard of such.
Unless this is a company that started from a publicly traded shell company, the equity they're offering you is unmarketable, it's not something you can sell on the open market to get the equivalent cash (however they compute that).
Assuming you ever talk to them again, ask them how you can turn the equity into cash and then look at that for traps (e.g. "we'll buy you out" is something that at best you can enforce in the courts, which is going to be hard for such a small amount, what you'd see after paying your legal costs).
Their attempt to discount it now says it's not a priced in the future offering, what they're probably saying is that "this is a great deal, $20K today will be worth $20X K tomorrow". That completely ignores the risk side of the equation, the likelihood that the equity will be worth less than $30K when you want to cash out (most likely it'll be worth $0).
The other thing to consider is that equity is cheap* compared to cash, after all that's why they're trying to pay you partly in it.
My strong guess is that either they're idiots or they're trying to cheat you; in either case I wouldn't touch them with a 10 foot pole. Given that you're making a "guaranteed" (well, your current job could go poof) $60K in cold hard cash today, they need to make you an offer that's much, much richer if the cash is less and they're trying to make up the difference with very risky equity.
NOTE: if you don't understand something like this, if it feels "weird", it's never out of line to ask what it's all about, how it works, why they are doing it, etc. Since they are offering something unusual, it is incumbent upon them to explain it such that there is no mystery about it to you.