This is an accepted solution.
It's not possible to pinpoint where it's coming from without checking your theme, however this is a potential solution:
1. Download this Google Chrome Extension: (you need to use Google Chrome): https://chrome.google.com/webstore/detail/shopify-theme-file-search/mhchmhfecfdpaifljcfebnlaiaphfkmb
2. In your Shopify Admin, go to Online Store > Themes > Edit Code
3. In the new box that appears with the extension (top right corner) search for the word you want to find. In this case, just the number: 2
4. It will show you in all files that the number 2 appears. You need to take a look at all of them and search for the isolated number 2.
It's for sure that this number 2 is in a file that you or your developer have edited before, that is a typo. Therefore by keeping that in mind it should be easier to narrow down where it could be.
Given the location, it's very likely to be sitting at the top of your collection.liquid template.