A cool-off period is a 7-day wait time that applies for both bonded DHX and the newly mined DHX. You won't be able to use the DHX during this cooling off period.
All newly mined DHX gets auto-bonded to your already-bonded DHX, and there is also a 7-day cool-off period before the mined DHX shows up in your bonded DHX.
There is 7-day cool off period to unbond any bonded DHX - meaning it takes 7 days before you can withdraw the DHX. So please be aware of this before bonding DHX.