ADDACS and AUDDIS advices use the same numbering sequence. Therefore, your AOSNs could be numbered sequentially across both types of reports.
For example, the ADDACS report has AOSNs 40000007, 40000008 and 40000012, and an AUDDIS report has AOSNS 40000009, 40000010 and 40000011.
The AOSNs are generated by Bacstel-IP, not by Experian Payments Gateway.