Gotcha, @KristianZdrav, thanks for confirming. Is it possible that some people filled out this form more than once? That could be the cause for 1000 submissions, but 800 new profiles.
If that doesn’t seem to be the answer, you can check your accounts Dev tools logs here: https://www.klaviyo.com/developer-tools/logs to see if that provides more info. Since you’re running custom forms, it’s likely that whenever somebody fills out the form, API calls are being made to Klaviyo that send us their data. Are you seeing any failed Bulk Subscribe Profiles calls? They should look like a request called “profile-subscription-bulk-create-jobs, and have a red error message next to them. If so, that means that these calls are failing to subscribe profiles. Clicking into the call would allow you to learn more about the error and figure out what needs to be done differently.
If that doesn’t seem to be the issue, your next step would be to either reach out to the team that designed these custom forms, or our support team at Klaviyo.com/support, so we can look into it further!