"Millionths", abbreviated "mths of a second" here for... reasons...

Known to the entire world, including American STEM people, as a microsecond.

Anything to avoid using the proper units, you wouldn't want the Americans audience to be enlightened wouldn't you.

What irks me is that they could have abbreviated "7mths of a second" to just "7us" while ADDING clarity!

7ms is 7 milliseconds. Unfortunately 7μs is difficult to type and there isn't a good universal way to abbreviate it in ascii.

Eh, 7us is fine.

I'm reminded of Grace Hopper's famous nanoseconds lecture: https://youtu.be/gYqF6-h9Cvg?t=78

1 ns * c = 1 ft, to put in perspective: 7 μs * c is 1.3 miles.

(Protip: just type "7 μs * c in miles" into Google)

7 μs is also the time it takes light to travel about 1,400 Ariana Grandes.

In which direction? Presumably side to side?

Due to relativity the length of Ariana Grande will appear to change such that all observers agree on the same speed of light.

But... https://en.wikipedia.org/wiki/Side_to_Side

Oh, I haven't watched that before.

Not quite. The article says hundreds of nanoseconds, which would be in the 10 millionths range. Or if you take the title literally, 143ns per image. That's in line with the fastest CCDs, so not unimaginable.