Alphabetic characters aren't allowed in the track number field. There are billions of vinyl LPs still existing in the world and any song from an LP cannot be listed properly while this bug exists.
This is due to the ID3 specifications for the track number: it has to be a numeric string. So unfortunately there is really not much we can do about. For more information, please see http://id3.org/Developer%20Information. FWIW: you can work around this restriction by adding the track number to the title.
Thank you. In a future release can another field be added that can be used for LP track numbers?
The ID3.org definition doesn't have such a field, but you can already use a user defined field (currently not read automatically by Amarok), or define a label. The custom field support is already tracked as a wish in bug 141991