Why did a past day recompute?

Because something that day depends on has changed. To recompute means nouz works the day out again. On the cost side, that can be a cost saved with a past start date, or a rule edited or deleted. It can also be a change to your shipping zones, or a new weight or packaging size.

On the store's side, it is an order that changed in Shopify after its day: cancelled, edited or marked as a test. The next sync works it out again on the order's own day. Changing the store's timezone recomputes everything with the new clock. A refund made today does not touch the old day. It lands on today.

A recompute runs the same P&L maths over the same facts. A day with none of these changes comes out exactly as it was. If a number moved and none of these explains it, please tell us. A statement that changes without a reason is not a statement.

It starts as soon as the change is saved or synced, and only on the days the change touches. While it runs, the P&L, the Overview and Insights say Updating the numbers. They keep the old figures until the new ones are ready, then switch by themselves.