I have two identical external monitors, which are Lenovo ThinkVision 27 inch 4K monitors.

I have them both connected via USB-C to my 2018 MacBook Pro 15 inch, with Radeon Pro 560X 4 GB.

However in display settings, one is shown as:

LEN P27u-10 Display 27-inch (3840 x 2160)

And the other one is:

LEN P27u-10 Display 30,5-inch (1920 x 1080).

Why does it detect wrong display size (30.5 inch) and wrong resolution?

  • 1
    1) What happens when you switch the cables? 2) What happens when you only connect #1? 3) What happens when you only connect #2? 4) What are the exact Serial Numbers and Model Numbers of both monitors? Commented Sep 19, 2019 at 15:09

1 Answer 1


I think the monitor can handle the first external display at the full resolution, but it cannot drive the second one at full-res, too. Thus it limits the available display options.

If you lowered the resolution on your built-in laptop display, you should see the third display be available at full res.

  • The 15" 2018 MBP can easily cope with 2 4K external monitors, in addition to its own screen.
    – benwiggy
    Commented Feb 21, 2022 at 19:00
  • You shouldn't have downvoted just on your opinion - I have see this happen in my own setups. I don't have two monitors available right now, otherwise I'd post a pic to prove it to you. For the sake of the community and 'fast readers' that won't check these comments, please remove the downvote as it's a relevant answer. Commented Feb 21, 2022 at 19:20

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