Small Group Participation - count only once

The Small Group Participation seems to be an area of confusion when we say count a person only once.  Here is the best way to think about this.  If you have 300 people who are worshiping on a regular basis and you want to know what portion or percentage of these folk are participating in a small group, you would only count them once.  So if you have 60 people involved in small groups, you have 20%  of the worshiping congregation participating.  We are not wanting to collect attendance in these small groups -- therefore we asked a person be counted only once.