Earlier this year after a friend installed a Garmin GDL 82, we flew near each other while he switched Anonymous Mode on and off to check its operation. His transponder is a GTX 327. I captured this ForeFlight screenshot showing him immediately after he switched Anonymous Mode off.
Note the two targets on top of one another, one showing his N-number and one showing "VFR". After several seconds the "VFR" target disappeared and only the N-number target showed. We tried this a few times (him switching between Anonymous Mode on and off) and two targets would show up from a few to several seconds until one dropped off. We attributed this to latency/overlapping data in the ATC system, until the older, stale data dropped from the system.