What drives the file extension on invoice attachments coming from IDR?

Summary:

We are sending scanned pdf invoice images to payables through IDR. The invoice attachments have strange file extensions. Example:

EQSG-DEV1_20230808111205BCCD32BE653F3CB52766A9DDE4286AA4_3370218_C6D64223.pd.pdf

Expectation is 'pdf' but instead it is '.pd.pdf'

Content (required):

We are sending scanned pdf invoice images to payables through IDR. The invoice attachments have strange file extensions. Example:

EQSG-DEV1_20230808111205BCCD32BE653F3CB52766A9DDE4286AA4_3370218_C6D64223.pd.pdf

Expectation is 'pdf' but instead it is '.pd.pdf'

Version (include the version you are using, if applicable):

23C (11.13.23.07.0)

Code Snippet (add any code snippets that support your topic, if applicable):