Dell UltraSharp 27 User Manual page 42

NOTE: Supports the DP MST feature. To make use of this feature, your PC
Graphics Card must be certified to at least DP1.2 with MST option.
NOTE: Remove the rubber plug when using DP out connector.
Connecting the USB-C Cable (A to C)
NOTE: This connection only data is available and no video. Need another
video connection for display.
Connecting the USB-C Cable (C to C) (Optional)
NOTE: This connection is only upstream available and no video. Need
another video connection for display.
42 | Setting Up the Monitor