Jandex reports the same revenue Klaviyo does, because it reads the same conversion metric your Klaviyo account already uses (your Placed Order metric, or whichever order metric your store is configured with).
Campaign and flow revenue is the value of orders attributed to that message inside Klaviyo's attribution window. A/B test revenue is the same idea, split out per variation so you can compare versions on dollars, not just engagement.
It is almost always because the wrong order metric is selected for the account. Open the account settings and confirm the conversion metric matches the one you trust in Klaviyo. Matching the metric resolves nearly every revenue mismatch.