How does the calculation differ for different types of conversions- uniques, totals and sessions? Let's say there are two events- transaction_initiated_event and transaction_success_event.
Ex: consider that a user intiated 5 transactions in a span of 10 minutes and first 3 transactions are successes and next 2 are failures.
For this, unique Users would be 1 & 1, total 5 & 3, Sessions depends on how you define sessions in your project - you can do event-triggered sessions, or timeout sessions, etc, so it really depends.