numbering storage controllers

[bohemian]

Is there anybody who can explain to me the "principle" of numbering of storage controllers used in the vboxmanage import command´s parameter "" --unit 11 --controller ... "" ??
User Guide page 113 (The example at the buttom of the page; the changing --controller´s value from 9 to 10 (from scsi to IDE) )

It is hard to understand for me relate to the fact there are 2 (primary/secondary) for IDE; 16 for scsi; 30 for SATA and relate to the clearly understand-able principle of numbering used in commands: hd, sataportcount, scsiport )

Thank you for your help.

[bohemian]

I think I resolved it.

The number mentioned behind --controller is the number of --unit that contains info about actuall controller and must be changed (if I want to do so) to the number of --unit that decribes the controller to which I want to change connection.
In that mentioned example the numbers are 9 for scsi and 10 for IDE.
I am I right ??????
Of course, the numbers are always different for particular VM depending to its configuration.