Don't worry about the speed of the whole group of words; focus on the speed from the previous to the target letter. In other words, if 'q' is the target letter, when you get to it, for example, the word 'acquire,' only worry about the speed and accuracy of getting from c to q. If you find that you aren't doing well with the passage (e.g. you've missed a bunch of 'q's), hit escape and start over before finishing the group/passage. Doing that keeps the algorithm from lowering the confidence score. Once that score starts going in reverse, it'll take several 'CONSECUTIVE SUCCESSFUL' passes through to get the score needed (1) to pass the letter.
I never worried about any letter other than the 'q.' Once I got to each q, I ensured I got it right, even if I had to hit escape on the whole passage. I learned that the hard way. It can be two steps forward and three steps back over and over and over.