excuse the double email; your answer made me understand that my question didn't make too much sense since a relay is not supposed to know the whole circuit.
11 Mar 15 14.25, Roger:
For example, it is quite reasonable that you have a bunch of circuits open for other people, but your relay has no "client" circuits because your Tor hasn't received any client-side application requests lately so it stopped building preemptive circuits.
Mattia