My connection pool graph doesn't go any higher than 12 connections and seems maxed out most of the time.

My DBCONFIG.XML file specifies a max pool size of 20 ~ it contains this:
<pool-min-size>20</pool-min-size>
<pool-max-size>20</pool-max-size>
Is my graph only showing 12 because that's how many actually got used ?(Therefore my system isn't really busy at all). Or should it be showing a scale up to 20? Is this throttled somehow at the database end? I was expecting the graph to show an X axis of 20.
thanks