AT+CMGD works very strange on SIM808 [temporary solved]

Is anyone has the same impression, that deleting sms on SIM808 is wierd ?

AT+CMGD=?

gives response:

+CMGD=(1-48),(1-4)

And this is somenthing I dont understand. What is this second numer (group of sms "READ","NOT READ" etc) for, when sms has continous numberation ?

You can't choose "second sms from unreaded" (which could be written as eg. AT+CMGD=2,2).

More.

If you send command AT+CMGD=1,4 (4 is for group "ALL") you can remove all smses, despite the number 1 (as for first sms on the list) is given.

Is this purposely work that way, or I don't understand how it should work.