It is most useful to restrict the salary range to match your experience level. Staffing agencies do not like to receive resumes from more senior level candidates, and search firms that work with senior level assignments do not want to receive resumes from candidates who are just starting out.
The salary the database lists for each recruiter is the minimum salary of assignments he/she accepts. You should choose a range that contains the salary you are seeking. For example if you are searching for a job that pays $75k per year, choose a salary range of $50-$100k.