It stood stuck at 0 for a while for me as well, before eventually updating. It's pretty crazy to see the amount of resources needed to load what is effectively a static page. I guess I shouldn't be too hard on a joke website but it's a bit symptomatic of the current state of the web these days.
There is a TODO in there to calculate the timestamp based on the tweet id rather than digging through the tweet iframe after it loads. If someone wants to submit a pull request for that it should speed things up tremendously. Bitwise manipulations in JS are annoying though so I haven't bothered.
The counter updates to 12 after the script runs, for myself. It is using a Twitter API at the back, so far as I can tell.