In short, every file that a page requests on your website is a hit. All you can do to stop this is enable a caching service like Cloudflare, or combine files to reduce hits. (In my opinion, do both)
Ok, let me give you an example:
On one page of your website, it requests 2 CSS files & 3 JS files. This creates 5 hits for that page. Now when you do the maths (all of the below is an exame)
5 (hits) x 10 (pages) x 300 (no. of visitors)
It adds up to quite a lot.