Are you using the Adobe default "Countries" or a custom evar you've named "Country"?
If you're using the default, it should be populating using internal adobe rules to determine where customers are coming from (more info about it, https://experienceleague.adobe.com/docs/analytics/components/dimensions/countries.html?lang=en). There shouldn't be a high amount of unspecifieds unless there is some error happening with the internal processing. Unspecified typically means that there isn't a value assigned in that particular instance.
If you're using a custom evar instead of the default dimension, then whatever processing rule/evar you're using to capture the information might not be doing so accurately. If you've got a processing rule or classification, then whatever it's acting on isn't being categorized properly, resulting in unspecified values.
