Sometime the resolution will be changed on the same OS with the same browser. I don’t know why?
This is an example on an PC with Firefox. Yes it is the same on other browsers or on mobile…
Sometinmes you can see this pictuere on the PC and(!) and mobile phone
(Sometimes on PC and moblie phone)
After creating a page or a report, you can see this kind of layout
(Mobile phone) 
(On PC)