If possible you can take 10% of the proposed sample size in your pilot study. Also remember to collect the data from the targeted population. All the best, Regards
The purpose of a pretest is usually twofold. 1. Test the data collection process and 2. To get information on the variability of the target population in order to estimate what sample size is needed for the study. #1 is often a pretest As long your pretest process does these 2 things it doesn't matter what the particular sample size is in the pretest phase. Best, D. Booth