According to a report by Forbes, Apple’s high-yield savings account attracted $990 million in deposits in its first four days.

The successful launch helped underscore Apple’s ability to further monetize its iPhone user base of more than a billion people. On the first day alone, Apple’s new savings account attracted nearly $400 million in deposits, according to Forbes, citing sources reviewed by Al Arabiya.net.

More than 240,000 savings accounts were opened in the first four days of launch, just 0.002% of Apple’s US iPhone users, based on the latest estimates from the company’s installed base.

And as more customers seek to take advantage of the high-interest-rate environment, Apple introduced a high-yield savings account last month.

The savings account is available to Apple Card customers through its partner Goldman Sachs and offers a 4.15% yield with no minimum deposit, no minimum balance requirement and no fees.

While Apple’s starting yield of 4.15% isn’t too high for high-yield savings accounts, there are a few things Apple does: “convenience.” iPhone users who already have an Apple Card can integrate the savings account into the iPhone Wallet app.