It says 00, meaning that I have more than 100 different tabs open on mobile in my Firefox browser! When I shop for things online I like to compare prices or quality of the same or similar items between stores, and I usually open a new window for each listing so I can compare them side by side, so sometimes that leads to dozens of tabs. I also have a habit of using open tabs as some people would use a bookmark or their watch later playlist. If I'm in the middle of reading an article or story, and cannot finish it, I just leave the window open to remind me to go back to it, same with a video I want to continue. If there's an event that I'm looking forward, and don't want to forget, then I have an open tab for that. Sometimes I clear out my tabs, but they always build back up eventually.