Not sure, as devices are setup differently -- but the word "debugging" suggests it:
If you are rooted, check whether the directory /data/tombstones
exists. If so, there might be some "tombstones" inside. Being root, you can delete them (they are owned by system
, and give no permissions whatsoever to other users).
Explanation: Tombstones
Tombstones are what the dead are covered with, and so it is here. On Linux/Unix known as "core dumps", this is what some apps leave behind when crashed to death: the process' memory dump for analysis by the developer. Only few applications throw tombstones, I guess they have to be explicitly enabled by the developer -- which might happen implicitly when toggling some debug flags.
Up to now, I didn't discover tombstones of that size (all I've seen was between ~30kB and ~250MB), but that doesn't mean they cannot be bigger...