You probably aren't doing anything wrong, Microsoft is though.
Your connection is 3G you say, but the Microsoft scale is based on GSM (2G). GSM gives a connection down to -113 dBm, but UMTS gives a connection down to -120 dBm. A different parameter is being measured as well, which makes the Microsoft implementation even less valid.
If we believe the Microsoft scale, your values of 1 - 4 are about -111 to -105 dBm.
In UMTS, this is quite a respectable signal.