Hey I got really carried away with these again and I might have one of the smallest displays ever.
It uses 6+1 segments the extra one being controlled by using a stronger strength cauldron to toggle the lower right segment which only needs to be de-powered for the "2"
These are easily chainable and can switch every 3 ticks A full 24 hour display would be only 23 blocks wide. 6x3 +5 spaces between numbers. Though it would look quite crowded so I guess this is totally useless 😀 It's probably possible to make it a little smaller so I won't say world's smallest but I think the Piston setup is pretty neat. The feed tape itself length-adjustable, tile-able and stackable which would be great for bigger storage applications maybe. Sorry for the tutorial I can't be bothered to edit on PS4.
If anyone knows how to wire the display better let me know because I want to eliminate the bottom blocks so it's truly 7 blocks tall