CTM and Subcontracting

Hi Experts, Kindly help on the following scenario (bold is what is requested to be clarified):

1. CTM ran, created the Subcon Preq – category ET,
2. CCR generated error code 182 - Schedule line without external number does not exist in R/3 (why?),
   1. no faulty queues,
   2. purchasing info in ECC material master is seen,
   3. number range in APO is good
   4. where to check the number range in ECC ?
   5. Any other pointer to check why this error comes?
      
3. Manual push in CCR goes to ECC with item category L, it gets firmed indicator in ECC,
   1. Is FIRMED indicator standard behaviour or some customising setting?
4. Ran CTM to delete the orders with transfer mode: “Transfer new and deleted orders”.
5. ET gets deleted in APO product view but nothing happens in ECC (item category is still L and firmed indicator is ON) - is it because of the firmed indicator in ECC (hope I am not sounding silly)?,
6. CCR now has the error code 181: Schedule line does not exist in APO, forcing me to push this subcon order in ECC to APO.
7. When pushed, it comes as normal Preq to product view – category AG! - ET is now AG ???

Because step 5 doesn't delete the order in ECC, I am forced to go for step 6 before taking a CTM run. If step 6 is not done but CTM is run, ET is created for the demand and then the step 6 would again give me AG which is kind of doubling up of supplies. This appears to me some customising setting not maintained rightly (or SAP is not designed rightly?) - can someone please throw light on this?

Thanks for the support,

Guru Charan