The file format is the same as what gets exported by the manager if you were to already have a list. If you import a single file you can then export it back out and it will get the same format. I believe the name and size are for display in the UI. The hash is used by the sensor in identifying the file.
The sensitivity is used in the response from the GTI servers to indicate "how dirty" the file is. The hash is used for identifying the file, the sensitivity is for determining what action should be taken with the file.