FIFO Inventory Tracking by Day - Not COGS

Hi team,

First time poster here. Having some difficulties tracking how long an item has been in inventory before being sold.

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If only part of the total orders get fulfilled using a perfect FIFO and carrying over remaining orders to the next part of the day with new orders coming in by day, I'm wondering what might be the best way to track this to find the average time spent in inventory before being sold by day and over a selected period.

Any experts out there might be able to help?

Cheers,
Nick