A start-up company based in the Cayman Islands is on track to raise more than $4 billion through a yearlong sale of digital tokens—the largest fundraising of its kind.

What buyers of the tokens still don’t know: how the company, block.one , will use the bulk of the windfall from its so-called initial coin offering.

If the company ends up raising that much by the offering’s expected closing date, this coming Friday, it would be more than twice the size of the next largest coin offering— Telegram Group Inc. raised $1.7 billion—and would be larger than all but one or two of the world’s initial public offerings on stock exchanges so far in 2018.

That a little known startup could raise so much money without a concrete plan for it speaks to trends in the topsy-turvy world of cryptocurrencies and views of the future of the online world.

The company didn’t reply to a request for comment.