[Level adjustment numbers clipped at high DPI]

The same as breyed, 192 dpi or 2x according to the diagnostics window (I'll paste the info below).   I'm actually running 2 monitors, the first at 200% and the second at 150% (both are UHD but they have different physical dimensions), but the issue is identical no matter which monitor I have the window on.  Thanks for looking into it!

 

Quote

Application    paint.net 4.0.17 (Final 4.17.6411.1908)
Build Date    Friday, July 21, 2017
Install type    Classic
    
Hardware accelerated rendering (GPU)    True
Animations    True
DPI    192.00 (2.00x scale)
Language    en-US
    
OS    Windows 10 x64 (10.0.10586.0)
.NET Runtime    4.0.30319.42000
Physical Memory    16,205 MB
    
CPU    Intel(R) Core(TM) i7-6700HQ CPU @ 2.60GHz
    Speed    ~2592 MHz
    Cores / Threads    4 / 8
    Features    DEP, SSE, SSE2, SSE3, SSSE3, SSE4_1, SSE4_2, XSAVE
    
Video Card    Intel(R) HD Graphics 530
    Dedicated Video RAM    128 MB
    Dedicated System RAM    0 MB
    Shared System RAM    8,102 MB
    Vendor ID    0x8086
    Device ID    0x191B
    Subsystem ID    0x06E41028
    Revision    6
    LUID    0x0000AEB7
    Flags    None
    Outputs    2
    
Video Card    NVIDIA GeForce GTX 960M
    Dedicated Video RAM    2,019 MB
    Dedicated System RAM    0 MB
    Shared System RAM    8,102 MB
    Vendor ID    0x10DE
    Device ID    0x139B
    Subsystem ID    0x06E41028
    Revision    162
    LUID    0x0000B22E
    Flags    None
    Outputs    0
    
Video Card    Microsoft Basic Render Driver
    Dedicated Video RAM    0 MB
    Dedicated System RAM    0 MB
    Shared System RAM    8,102 MB
    Vendor ID    0x1414
    Device ID    0x008C
    Subsystem ID    0x00000000
    Revision    0
    LUID    0x0000B1F5
    Flags    Software
    Outputs    0

 

[Level adjustment numbers clipped at high DPI]

I'm having the same issue.  Running 4.0.17.  No matter how big you make the levels window, the numerical displays are cut off.