I believe this may be a "bug" or "unplanned randomness in execution".
All of my SC items have an "Expected Delivery Time" set to blank - i.e. never set to anything. And yet the column in the list is showing a seemingly random number of days for some, blank for others, and text entered into the field on others - e.g. "N/A".
Can anyone else confirm this behaviour and/or tell me how to fix it?