Does this mean that someone downloaded the game's source code?
I don't think this is linked to people playing the game, since the game starts as someone clicks on the page each click will be the equivalent of a gameplay, very curious what this download statistic means.

Depending on account settings, games do not start automatically.

Technically, your game is downloaded every time, someone plays it. Of course there is hopefully caching, so someone playing it twice will only download it once.

If the chart only displays itch-app activity, it is a useless chart. But I cannot answer your question what those numbers mean.

Don't you have page view chart somewhere, to get more information?