To determine the number of corner points to use in a power and sample size analysis for a 2-level design or a Plackett-Burman design, look at a summary table of 2-level factorial designs. You need to specify the appropriate number of corner points given the number of factors. For example, for a 6 factor full factorial design you would have 64 corner points. However, for a 6 factor fractional factorial design, you can have either 8, 16, or 32 corner points.
For a Plackett-Burman design, the number of corner points must be greater than the number of factors.