Maybe I didn't read the site thoroughly enough but... how do we know that they are doing their part of the bargain? How do we/they measure how much carbon is effectively removed from the atmosphere?
My thoughts too. How do we know it's not just a website? An annual, independent auditor report would be nice, at least confirming their number of subscribers and estimating the capacity of their chemical process.
Climeworks is a Swiss startup in business since 2003; they have built multiple pilot plants in Switzerland, and are well known here. See e.g. https://www.climeworks.com/about/