Any manufacturer assigned an individual manufacturing quota for any basic class pursuant to § 1303.23 may at any time abandon his right to manufacture all or any part of such quota by filing with the Drug & Chemical Evaluation Section a written notice of such abandonment, stating the name and Administration Controlled Substances Code Number, as set forth in part 1308 of this chapter, of the substance and the amount which he has chosen not to manufacture. The Administrator may, in his discretion, allocate such amount among the other manufacturers in proportion to their respective quotas.