Your certificate history shows that you used to have one certificate that covered both liefseva.nl and www.liefseva.nl, but now have two separate certificates from Let's Encrypt, one for each of the names. Also, you now have certificates from ZeroSSL, and your screenshot above shows that that's the one you're actually using.
So, that's why you got the email: Your certificate covering both names is expiring, and (as the email says in it, after the portion you quoted) if you add or remove names that's a "different" certificate so you're getting expiration notices for the old one. If you're confident that your server is now sending the right certificates, then the reminder can be safely ignored. It is a little weird to be using both ZeroSSL and Let's Encrypt, though, so you may want to ensure that your systems are doing what you expect.
Some other resources that might help: