Looked at CO2 calculators again. Today: the tomorrow bank. Well, well, well…
First of all, it's not their calculator. It's a third party company, https://ecolytiq.com/, a company just happening to work on "hyper-personalised financial products".
Their "ecoAware" product tries to calculate how much CO2 your activities have emitted. The data they provide in their "Open Sustainability Registry" (which is a MediaWiki) is mainly transport data, data from the US and "number of people" data.
Thia is their "statical data collection": https://wiki.euosr.com/Sources_Overview
Their main customers according to their website is the "Tomorrow bank", a German startup.
Further their "Company and Merchant Registry", which might could provide reasonable data, is "COMMING SOON" since 14 July 2021.
https://wiki.euosr.com/Company_and_Merchant_Registry
TL;DR: they can make up any numbers by using "statistics" and try to calculate it down to an individual, which once again is quite pointless.