Question

What do the warranties for SSL certificates mean? What is covered by them?

Answer

SSL certificates services include a limited Warranty to provide your site extra assurance that your site is safe to conduct online business.

Warranty is payable to your visitors who rely on the SSL and who incur losses resulting directly from an online card transaction as a result of a mis-issued SSL certificate.
Warranties start at $10,000 (most DV certificates) and go up to $50,000, $100,000, $250,000+ for OV and EV.

Certification authority will refund you in the event something goes wrong on their end and the website will be hijacked that is why you should feel confident with an SSL certificate.
If anything goes wrong that causes you to lose the money - you are covered.