I'm afraid that GDB is a bit of a geek's tool, and I'm not competent to teach anyone else how to use it. I only use it within the confines of the development system, where it's integrated in a much more friendly fashion.
Looking back over the history of this issue, I'm tempted to conclude that there's something about the DGN2200 which DSLstats isn't handling correctly. Could you copy the contents of Telnet data --> Connection stats to me, and I'll check whether there's anything there which I'm missing.
By the way, I'm just about to release v3.7. It won't fix your problem, but I didn't want to hold it up. If I do locate the source of your problem I'll upload a fix immediately.