On the STS Disk 15 (Back & Biceps) worksheet, the barbell deadlifts and the preacher curl are both missing the line for the 8 rep set for each exercise.
I checked both the users guide and the online workout card and both have both of these exercises listed correctly. The third set is listed as TF which means "to failure" - 8 is just the minimum goal. You should do the third set until failure.