My MacBook Pro thinks my 32 inch monitor is 27 inches?

Hi!, I've just purchased a 32 inch 4K monitor (LG 32UK550-B32UK550-B) and at first the display section in ' About my Mac' recognised it as 27inches and was displaying at 30 Hz. I bought and connected a usb-c to DisplayPort cable from Officeworks and hooked it up. And although the display has improved and the refresh rate is 60 Hz, Its not exactly what I'm expecting so I checked the settings and it still recognises the 32 inch monitor as 27 inches? Is there a way to fix this or is there recommended settings that anyone would give me? thanks heaps! - Ps I have the 15 inch MacBook Pro from December 2018 -