Hi Rajesh,
Yes, this is expected. The Opt-out indicators simply look at any URL with a category of Opt-Out (see indicator documentation below):
https://experienceleague.adobe.com/en/docs/campaign-classic/using/reporting/reports-on-deliveries/indicator-calculation
As for getting unique opt-outs. There really isn't an attribute for it, since the idea of opting out is that there should be one link that a recipient clicks once and is opted out. There really shouldn't be duplicate opt-outs, but if there are, simply create a workflow with a dedupe activity and target duplicates based on recipients who were emailed (broadlogrcp). You'll also likely need to link to the trackinglogrcp and url tables if you want to really drill into the URL details.
Regards,
Craig