Scaling issue on multil monitors

[On Holiday]

Setup:

Top screen - Philips 4K TV - 3840x2160
Bottom Left - Dell - 2560x1440
Right screen (irrelevant) 2560x1080

So when I move a window from my main Dell to the Top Screen it just goes too big.. How can I stop this?

Thanks in advance.

 

[On Holiday]

Ahhh nice one dude.

I presumed that option was persistent for all monitors, but I clicked the 4K screen in there and that was set to 300%.

Thanks a lot, been bugging me since I got this TV!