Which post gets the credit when a lead saw several posts before messaging?

The one that started the conversation, unless the person names a different post. If someone replies to a story, the story gets it. If they type "loved your reel about the patio", that reel gets it, even if a story opened the chat. Earlier posts they saw get noted as influence, not credit.

Agencies sometimes try to split credit across every post a customer might have seen. On Instagram you rarely know what that list is, so the split ends up being invented. One clear rule works better.

A rule that holds up in a client meeting:

• What the customer says beats what the data says. If they tell you which post made them reach out, use it.
• Otherwise, the post that opened the thread. Story replies, shared posts, ad clicks and comment replies all carry that link automatically.
• Otherwise, unknown. Don't guess the most recent post. An honest "unknown" row keeps the rest of the report believable.

If a client asks about the bigger picture ("didn't our whole series do this?"), answer it alongside the credited numbers: show which pieces of the series the credited leads came from. That's more convincing than a percentage model nobody can check.

The full method is in How Agencies Prove Instagram Brings In Leads (When Google Analytics Can’t See Them).