When we say “burn 25% of Nervos CKBytes in genesis block”, the 8.4 billion CKBytes will be sent to an address owned by Satoshi. This essentially means that no one will move or touch those tokens (unless Satoshi comes back and that would be another story :P).
The 8.4 billion CKBytes will not disappear (as normally you will assume burned=disappear), more importantly, it will have an impact on the secondary issuance.
The Nervos Foundation will write data to occupy 15% of the CKBytes in the genesis block, while leaving the other 10% CKBytes of the genesis block liquid (not being locked into NervosDAO!)