It's attached to post 2412
My browser is giving me a slightly different look then yours.
Click that arrow to the right of "cumulative confirmed cases" and I suspect it will cycle through the tabs that are in that frame.
ETA: Yeah, It's an artifact of Firefox. Chrome, IE, and Edge all show it as I think it's designed with Tabs. I don't have Waterfox on this laptop to check it. In Firefox, those left/right arrows will cycle through the tabs that you can't see. Each frame has a couple options on it. For example, where yours says "admin0" under the cases by country, you can cycle to "admin1" which is cases by state/province, or "admin2" which is cases by US county. For some reason on your screnshot the tabs exist under the "total deaths" frame, and you can but none of the rest. Weird. Firefox seems to have more then it's share of weird little glitches in web pages
ETA Again: Oooooh. It's a screensize thing. If firefox thinks the tabs will be too small it renders it as the banner with arrows. I'm running 1920x1080 and if Firefox is a window it shows what you have. If I go full screen I see what's attached to this post.