When talking about your prior experience and accomplishments, it is important to be as specific as possible. Mention dates whenever possible so that the hiring manager gets a clear picture of how your job responsibilities have grown and changed over time.
Instead of saying “I worked as an administrative assistant for the agency, then as a front line manager” say “From 1/1999 to 6/2000 I worked as an administrative assistant and in 6/2000 I was promoted to assistant manager.” Showing direction and advancement in your career is a great way to communicate your capable and qualified to move up.