I think I understand, LePousson.
The different options on the Alerts screen are "OR", not "AND", so with Range ticked, you will get an alert for all aircraft reporting as being within that range. It doesn't matter that you also have an alert for A3* - that will trigger alerts for all A3*s, no matter what their range from EGLL.
We have a long-standing hope that alerts will be changed to be much more flexible in a future software release.
I hope that's answered your question.
Rod