http://sparrowa7io5pz6ud3ehqzosvepbxbxt2zphmkjsylp2zgxooko23pqd.onion/docs/coldcard-wallet.html
At this point, it’s a good idea to add additional entropy (randomness), just to be sure that your seed can only have been created once.
To do this, get a normal 6-sided dice. Then press 4 on the Coldcard.
Roll the dice and press the number 1-6 on the Coldcard that comes up on the dice roll.
Do this 100 times, and you can be sure that your seed is yours and yours alone!