An uncursed scroll of enchant armor that targets a +0 (or below?) piece of armor will raise its enchantment the same amount as it would if it were blessed (1 to 3 points).

The purpose of this is to incentivize players using them earlier in the game, and therefore smoothing out the gain in AC over time, rather than hoarding them and only ever using them when blessed and on ascension kit items, which tends to mean a huge gain in AC all at once. This isn’t intended to make using them earlier the clearly best strategy, just to make it a more balanced choice.