Are you applying in this cycle? If not, get yourself 30 more hours of shadowing. Volunteering and clinical training doesn't count as shadowing. Let someone follow them around on a 8-12 hour shift. Repeat 2 more times with different specialties.
Of course, any essay or interviewer that asks "why medicine" you are free to include experiences other than shadowing when formulating a response.
The shadowing item in the Work & Experiences section of the application is a quick and dirty way for an application assessor to size up your application and you don't want to get dinged by someone who makes a cursory glance at "shadowing" and decides that you are too unfamiliar with what a physician does (particularly if your paid work experience is pre-hospital) to be considered a viable applicant for that school. (Remember, some schools interview <15% of all applicants, the winnowing is fierce).