If you find that the number of leads that's reported in the "reporting" section of Thrive Leads doesn't match that of your autoresponder then you might start to worry that leads are being dropped.
In reality, there are actually a number of reasons why leads might appear in the Leads reporting dashboard and not in your autoresponder:
Double opt-in - Thrive Leads counts conversions as soon as the form is submitted whereas most autoresponder services require double opt-in confirmation before the lead is registered. Double opt-in means that the autoresponder sends an email to the subscriber asking them to confirm the subscription before the conversion is recorded.
Obviously, it's quite common for people who sign up to not confirm by email. Maybe the subscriber used an incorrect email address, the email is getting blocked by a spam house or they just simply changed their mind about subscribing when the email landed in their inbox. If any of the above occurs, the conversion would still show in Thrive Leads but no in the autoresponder.
Server time differences - The time of your server is probably different from that of the time of the server that your autoresponder is using, therefore producing a daily report in both places will not be for the same period of time leading to a mismatch in the numbers.
Client-Side Validation - Thrive Leads allows you to add validation to ensure that the data you're receiving is correct. For instance, you can add "required fields" or a check to make sure that the email address is a valid one.
Without these checks, it's possible for people to submit empty fields that will be registered as a conversion - of course, your autoresponder will refuse those leads, even though in Thrive Leads they will be registered as a conversion.
The easy way to make sure this doesn't happen is to set up validation parameters in the control panel when you connect to your autoresponder.
The true number of leads that you've captured that's ready for receiving emails is the figure that's shown in your autoresponder.
What does this mean in the Context of Testing?
When you're split testing, absolute values have little importance. If you get 50 conversions from the same number of traffic as another form that got 15 conversions, the "50" is not important as a number by itself. What's important is that it's 35 conversions more than the alternative.
Therefore, I encourage you not to focus on comparing the reporting stats between your autoresponder and what shows in your Thrive Leads dashboard beyond basic checking to make sure the integration is correct.
Instead, work on the premise that all things outside of your control (such as the percentage of people that sign up for your mailing list but don't confirm their subscription in the double opt-in process) are constants for each variation and simply focus on how forms perform in comparison to one another.
If you keep filtering to choose the highest performer, your conversion rate will continue to improve and over time you'll grow your subscriber list a lot faster.