Its says that for me at first, then it changes to the correct number after it loads the icons.

That's because it's calculating it on the fly for every request; it's not caching it apparently. I don't understand why something like this wouldn't be server-rendered and cached.

Because when I first built it, it was only a site I botched together really quickly for a handful of icons I made. And I haven't had the time to re-make it, which is what I'm doing right now.

That is precisely the problem

SPA was a mistake.

Wonder how SPAs will load on Intel after developers get used to building them on M1.

Why would it be any different? Isn't the point of web that it doesn't matter what hardware you're on?

Ideally, yes. But alas, many parts of the web do not run well on all hardware. There is an extremely wide range of devices in use on the internet, and western developers are often in the 1%.