The quantity fixed for the annual quota period for each serial number shall be divided among four subperiods, as follows:

1. (a)

   25 % from 1 January to 31 March;

2. (b)

   25 % from 1 April to 30 June;

3. (c)

   25 % from 1 July to 30 September;

4. (d)

   25 % from 1 October to 31 December.