Yeah its 4k, but on a 24" monitor would you really be able to tell it apart from 1440p? Probably not as much as youd think.
Also, running DSR really wont give you the proper feel for 4k on 24".
I would say, if you can, look at some monitors in a store, but generally I wouldnt go 4k under something like 27", 24-27 at 1440p is a good range as well.