How To Identify A Transcode ? Options

[myaudio]

I have recently downloaded an audio file [ mp3 ].
The details of the file are as follows [ audio idetifier software used ] :

Average Bitrate : 249 Kbps.
Bitrate : 248 Kbps.
Encoder : LAME 3.97b.
Encoding Options : V0:preset extreme(fast mode).

In real situations do we have 248 Kbps audio files.
Is the above file have been transcoded ?

I have come to know we can do some spectral analysis using adobe audition, we can know whether an audio file has been transcoded.

I am still googling for the characteristics of various audio Kbps files.

I request members to suggest me some links where i can learn something about various mp3 Kbps formats.

Any help would be helpful for me.

Thank You.