Black to Turquoise in a week! Woo! Congrats! Overshooting the shock FC by a little isn't likely to harm anything assuming a reliable CYA reading - but - if you want to be on the extra cautious side on the evening readings you can add like 75% of whatever pool math says, wait 15-30 mins with pump running, retest, and then see how close you are, add a little more if needed. Slower than the one step, but if it puts your mind at ease, it could be worth it. It is what I do when I add acid if I'm between readings on the block. Prevents overshoots.