Example from https://commons.wikimedia.org/wiki/Category:Computer_architecture_diagrams:

• Computer memory‎ (15 C, 76 F)
• Microprocessor diagrams‎ (2 C, 25 F)

Unlike what a casual user might think, these bear no relation to Celsius or Fahrenheit. Rather these are obscure single-letter abbreviations meant to signify "subCategories" and "Files", where "file" generally means a photo, illustration, video, or other user-uploaded media file.

I did a little experimenting with putting normal words here:

I personally think this makes a net-improvement. But I also see that with the current current design (in terms of text color, font size, position, and line wrapping) it does feel a bit messy.

There is also a tooltip, but I think from a UX perspective one can consider these tooltips to be non-existent and are not an acceptable means of communicating essential information to the user. Not to mention that they aren't discoverable (why would anyone try to hover them?), they don't work on mobile, don't work via keyboard navigation, require precise mouse motor-control, and might not be very accessible when scanning the page by other means.