As explained in the Anki examples:
-
If you just enter a number, it will change only the card’s due date and won’t be random.
Example: If you enter “7”, the card will be due in one week. -
If you enter a number followed by “!”, it will change both the due date and the card’s interval.
Example: If you enter “7!”, the card will be due in one week, and its interval will also be set to 7 days. -
If you enter a range, the due date will be randomized within that range.
Example: If you enter “1-7”, the card will be due on a random day between 1 and 7.
I hope this clarifies it for you! 
If you think this is a suitable option for your case, you can restore a backup to recover your data from a specific date: How to Restore from Backup