It would be nice to improve the "Backup Codes" option from 8 numbers to 12 numbers.

Example: 97997695 > 520184887438

These should probably mean than in a online attack scenario (assuming one thousand guesses per second) it should jump from 1.29 days for 8 numbers, to 35.33 years for the 12 numbers.

I think everyone would feel a little less concern with random online guessing with these small improvement.

For human usability maybe use dashes between numbers: 520184887438 would look: 5201-8488-7438