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).
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...