The certificate chain is a list of certificates that are used to authenticate an entity. The chain begins with the certificate of that entity. Each certificate in the chain is signed by the entity that is identified by the next certificate in the chain. The chain terminates with a root CA certificate.
This knowledge document covers how TIM handles SSL/TLS certificate chains.
A certification chain is normally part of certificate creation and is not relevant for TIM to monitor traffic. Tim needs only the actual private key corresponding to the Webserver certificate. This will be used to decrypt HTTPS (SSL/TLS) traffic regardless of how many certificates are in the chain.