Client and Game resolution.

[NizzyStorm]

Hello, people. I have a technical question which i am unsure of and looking for support about it if possible. 

So I got a 4K monitor recently. But it's kind of weird. 

 

So, as you can see in the screenshot below I have 1080p and then it goes straight to 4K. The problem is, I would like to play in a resolution a bit higher than 1080 but 4K is too high and in know other people have resolutions in between these like 2560x1440 But I don't. Any idea's why? My only assumption is that it's Hardware related, like processor or graphics but I don't even think so because they can support a resolution higher than what I want to play in so that wouldn't make any sense.