Unfortunately, we can't guarantee Youtube views, likes, subscriptions, and comments. We can guarantee that we facilitate those numbers as far as we can detect, but it's up to Youtube to determine if any action was a valid one. In some cases we can detect if Youtube has invalidated the action, when this happens we will return you your credits. In some cases, we can't validate the action afterward, like views, and in some cases, we get false validations because of the way Youtube invalidated this action, like subscriptions. For as long as a campaign is running/active we'll check views, likes, subscriptions, or comments.
To understand this better we will give you some explanation about how things work:
We guarantee that we will send the number of unique users to your video just like you specified. These users will view your videos as long as you specify, if they watch your video shorter we will detect that and mark this view as invalid. We will mark the view as available again and the viewer won't receive credits for the view. So no credits lost in your campaign and in the best case Youtube will still detect as a valid view and you got a free view from us. Unfortunately, we can't detect if a view was marked as invalid and removed later by Youtube. It is important to understand you buy viewers, not a guaranteed number of valid Youtube views.
Read more about the view algorithm here
With comments, it's a bit different, we can detect if a comment from a user is still there and we can detect when it is removed. When this happens we return you your credits by returning one comment to the campaign. Please keep in mind that this check is only active for running campaigns.
We can't verify likes after they are marked as done within your campaign. There is no way we can see who did place a specific Like via our system so, therefore, we can't verify likes afterward.
Subscriptions are just like comments, so we can validate subscriptions and we will as long as a campaign is active. One side note on subscription checks is that Youtube not always delete the subscription when it's marked as invalid. They will only remove them from the statistics, so they don't count. The downside of this as that we still get validated checks on these users, so we can't always see if they are marked as invalid.