In that case, maybe the phone was misreporting internal storage, or was giving a total of internal SD card storage and the other partitions. (It could also be that it was counting the total of the internal SD card; notice the .android_secure file on the screenshot in your first post. Apps and data can be stored there as well as the /data partition.)
The Bionic has 16 GB of storage, and that's it. 8 GB are set aside for the internal sd card, 4 GB for the /data partition, and 4 GB for something else (not sure - probably the other internal partitions, plus all of the stuff the Bionic needed when it was docked with the old webtop stuff that Moto used to sell). It's all carved from that 16 GB - the internal sd card is not an extra 8 GB, but 8 GB of the total 16 GB storage.
Again, I'll point you to this article:
The Droid Bionic has 16GB of internal storage, but you can't have it all | Android Central with a screenshot of the storage settings. The first item, "Application storage", is the /data partition, and it shows 3.52 GB available out of the total 4 GB that was partitioned to /data. (The "internal storage" in that screenshot is the internal sd card.) That's the way the phone is partitioned.
See also
https://motorola-global-portal.custhelp.com/app/answers/detail/a_id/71223/related/1