No, it's not real money. In this case, convertable notes are loans backed by stock. That's why the debt is valued so highly. The notes are still for the same amount of stock, but the value of that stock is inflated beyond reason. Either way, Anthropic is not on the hook for the cash value of the stock, just the stock itself.

This debt is essentially noting that Anthropic does not own all of this stock on their books, but converting it into cash-value to do so. If someone were to buy the company, like via an IPO, it would be important for them to understand how much of the comapny's valuation is actually owned by the company vs other entities.

It is literally not real money. It is the value of shares that anthropic owes to its lenders. In the event its market value crashes, so does the majority of that debt.

These notes can eventually convert into company shares. Anthropic's valuation increases dramatically. The value of the investors' conversion rights increases too. Accounting rules require Anthropic to recognise that increase as an expense. In other words, Anthropic's rising valuation can actually create a reported accounting loss. An important distinction: This is not necessarily money leaving Anthropic's bank account. It is a non-cash accounting adjustment reflecting the increased value of financial obligations tied to future shares. Think of it this way: You borrow money and agree that the lender can convert the debt into shares in your business. Your business becomes much more valuable. Those conversion rights become more valuable to the lender. You now have a larger accounting liability, even though you haven't paid the lender anything extra in cash. That's broadly what happened.