VOTT allows you to fine tune the bounding boxes using the arrow keys in a few different ways. While a region is selected:
Tuning visual display of regions:
Use the number keys to quickly tag a selected region
(Only works for single digits 0-9)
Changing Tags
To change which tags are mapped to the hotkeys, hold Shift+(0-9) and click on the tag that you want to assign to that hotkey
To delete tags from list, use ctrl+left click on the tag you want removed. It will remove the tag from the list and untag any images that use that tag.