Obtain and check the distributor's spec sheet.
Files to DG SpotCentral for Distribution File Specs:
Extreme Reach spec sheet:
Just be aware that "general" audio levels (as read on a meter) are not the full story in broadcast.
"Loudness" is part of QC and a little more complex to control.
Compression was a technique that allowed audio to appear fine on a meter eg-12db...but the loudness payload "hidden" in the track was excessive.