> Up to 19 hours of battery life based on typical Surface device usage. Testing conducted by Microsoft in February 2021 using preproduction software and preproduction 13.5” AMD Ryzen™ 5 Microsoft Surface® Edition processor, 8GB RAM device. Testing consisted of full battery discharge with a mixture of active use and modern standby. The active use portion consists of (1) a web browsing test accessing 8 popular websites over multiple open tabs, (2) a productivity test utilizing Microsoft Word, PowerPoint, Excel and Outlook, and (3) a portion of time with the device in use with idle applications. All settings were default except screen brightness was set to 150nits with Auto-Brightness disabled. Wi-Fi was connected to a network.
I think the key in there is "modern standby." What is the ratio of standby to active use? That and 150nits brightness, though that is common for a lot of battery tests. (I personally like 250-300 even indoors.)