What's the mistake? - unattend.xml

I am trying to create two partitions using Sim Tool as follows:
- 1 active primary
- 1 logical in an extended space - using the remaining size for disk 0

But I want to model a unattend.xml to automatically wiping disk 0 - and let the setup create the partitions but every time the setup gives me an error message saying “Couldn't extend a partition on disk 0....not supported for this partition or volume. Error 0x80300024.” But the problem I’m facing is I don’t have any idea what is the size of the harddisk and hence I am not able to specify the size of the logical/extended partition.

Can somebody help me out please?

I would like to know whether you trying to format the extended volume or is it logical drive? Anyways, I will suggest you to simply format the logical drive and when you do so, the numbering will appear as to be the extended drive.