You may sometimes notice a difference between the number of "Users Entered" into your giveaway and the number of comments on your Instagram post. There could be a few reasons for this:
The same user posted multiple comments. These can still count as bonus (multiple) entries based on your giveaway criteria but will only count as one unique user.
The comments are identified as spam by Instagram or came from accounts that Instagram has banned. This helps ensure your true followers are more likely to win.
Any comments made by you (the post author) don’t count as entries but count towards your Instagram comment count.
The difference between your number of comments on Instagram and your users entered is nothing to worry about, it's just part of quality control to ensure your followers get fair and secure giveaways.