Defence dice is targets, in this case 6 for the banner and 1 for the site (sites are all 1 die). You add Warbands to the total rolled, so a fixed +5 (Warbands do not provide defence dice).
You rolled X2, X2, 2, 1, 0, 0, 0 for 12, then +5 for Warbands.
But it had to be done… or to put it differently: I couldn’t see another way.