a.sign seal qualified is a qualified electonic seal in accordance with the eIDAS regulation (https://eur-lex.europa.eu/eli/reg/2014/910/oj, Section 5, Article 38, Qualified certificates for electronic seals)
a.sign seal qualified is a remote signature, therefore the seal private key is stored in a hardware security module in the A-Trust data center.
User Manual: User_Manual_a.sign_Seal_qualified