The 2mb limit is applied to each file field separately.
Be aware of the other restrictions on file uploading though. For example the "post_max_size" setting. This restricts the size of the entire forms post collection, and must be created than the "upload_max_filesize".
In your case with three file fields and a 2mb limit on upload_max_filesize, the post_max_size will need to be at least 6.5 or 7mb.
See the following for info on settings that effect file uploads: