Displays Preferences shows SCALED resolutions. These are NOT the Hardware resolutions you display is set to. These are effective resolutions for TEXT when displayed on that display when you select Scaled.
They are intended to be a convenience for you, but they often cause concern and outright alarm instead.
To see the ACTUAL resolution your display is set to use:
Menu > about this Mac > (system report) > Graphics & Displays
Select your display and scroll around until you see two items.
The first is self explanatory: 'Resolution:' 2560 by 1080
This is the hardware resolution at which your display is operating. Graphics are drawn at this Actual Resolution. But there is a problem -- If text were displayed at the Actual Resolution, on HiDPI displays, it would be microscopic and unreadable.
The second resolution shown is 'User Interface Looks like:' this reveals the apparent size of text displayed on your display after scaling is applied ONLY to textual items.
Text is rendered at full resolution, then SCALED by the display Hardware by a factor (like 1.2 or 1.5, or 2.0) before it is aded to the display buffer. This makes it fully readable, yet maintains crisp edges that would be lost otherwise.