How downloaded bytes are measured on Firebase Hosting and why is it not proportinal to number of visitor?

I am using Firebase Hosting and am following the usages regularly to see how many downloads occur per day as I'm using spark plan which has a data transfer limit of 360MB/day. But I couldn't understand how data transfer is measured and why it is not the right proportion. Visitor numbers and usages are below:

7th of March: 41 visitors, 339.5 MB
4th of March: 21 visitors, 79.5MB

What might be the reasons for that? How is it vary?

Solution

There could be many reasons for this. The first few that pop to mind:

The visitors on March 4 could have visited less of your site than the visitors on March 7.
The visitors on March 7 could have used browsers that (pre)load more parts of the site.
The visitors on March 4 could have been repeat visitors, who already had part of your site in their browser cache.

But as said, these are just a few of an incredibly large swath of possible reasons.

If you want to learn more about how users browse your site, I recommend either enabling analytics or (less intrusive) enable and check access logs and looking for patterns (which are also hugely diverse).