Alphabet Inc.’s Google gives Apple Inc. a 36% share of the revenue earned via advertising from searches in the Safari browser to be the default search engine on Macs, iPhones and iPads, chief executive officer Sundar Pichai confirmed.

Pichai took the witness stand Tuesday in an antitrust trial over the Google Play app store in San Francisco federal court brought by Fortnite maker Epic Games Inc.

The showdown threatens billions of dollars in revenue generated by Alphabet’s app marketplace. Epic claims Google has monopolized the Android app distribution market for more than a decade by striking side deals to pay off rivals and uses its “vast resources to snuff out all competition.” If Alphabet loses, it could be forced to open the door for payment and app distribution methods outside its own app store.

Read More: Google Play Trial to Test Alphabet’s App Marketplace Power

The CEO said he didn’t know the percentage shared with Samsung Electronics Co., the largest maker of Android smartphones. Epic’s attorney Lauren Moskowitz said the revenue share was 16%.

When asked if he agrees that Samsung gets “less than half of what Google pays Apple for search revenue,” Pichai said Samsung benefits from using Android and that it’s “apples and oranges.”

Google, Apple and Samsung requested to keep confidential the terms of their revenue share deals, but US District Judge James Donato who is overseeing the jury trial ruled that the terms could be shared publicly.

Pichai confirmed the Apple revenue-share figure after Alphabet’s main economic expert in a separate Justice Department antitrust trial in Washington inadvertently revealed it Monday. The disclosure caused Google’s main litigator to visibly cringe when he said the number, which was supposed to be confidential.

A Google executive testified Monday in the San Francisco trial that the search giant agreed to pay Samsung $8 billion over four years to make its search engine, voice assistant and Play Store the default on the company’s mobile devices.

--With assistance from Malathi Nayak and Aisha Counts.