You stop offering a new customer a unit that is already reserved for another order, because you start separating what you can sell from what is already committed.

This tutor teaches a simple piece of math: the physical stock of a product is always the sum of available plus reserved. A reserved unit still sits physically in the store, but it can't be offered to whoever just walked in.

You arrive with your store's best-selling product, and the tutor asks, one number at a time, for the physical quantity, the available quantity, and the reserved quantity. Then it asks you to count that product for real and compare it against the three numbers you gave. From that comparison, it finds out whether you treat everything as one single quantity, whether you split available from reserved but forget to update both together, or whether the count already matches.

You leave the tutoring with one product counted and verified. If the math didn't hold up, the tutor doesn't fix it for you: it helps you find where the update was left half done, and asks you to log a real stock movement, with both parts corrected, to confirm the count now matches.

You pick the store's best-selling product right now, and the tutor asks one thing at a time: the physical quantity of that product, the available quantity, and the reserved quantity. Only after that does it ask you to count the product for real and compare it with what you answered.

It compares this to a product held on the pickup shelf for a customer who already paid a deposit: the item is right there, in plain sight, but nobody hands it to whoever walks in next. A reserved unit works the same way, present in the store, out of circulation for sale. If you say you'd offer that unit to a new customer, the tutor goes back and asks what happens to the order that already had that reservation.

At the end, it asks you to rebuild the math in your own words: why physical equals available plus reserved, and why only the available part can be offered to a new customer. The final task asks for the log of a real movement, like a sale, a reservation, or a delivery, updating both parts, followed by a recount of the same product. When you come back, the tutor asks what changed in stock and what the recount showed, and fixes only the part that was left unupdated.

You make the physical count match what you can actually sell

Before, you had no clear explanation for the gap between what was counted and what the store thought it had available. With the split between available and reserved, and the rule that physical is always the sum of both, every count now has math that holds up. This cuts the time spent looking for a product that "disappeared" when it was actually reserved.

You stop offering new customers a product someone already claimed

Before, you could offer a reserved unit to whoever asked next, because the available number didn't exclude what was already committed. With reservation split from available, whoever's answering only offers what can really be sold right now. This cuts the rework of walking back a promise made to a new customer for a product that already belonged to another order.

You stop leaving stock updates half done

Before, you would sometimes update only one of the two numbers after a sale, a reservation, or a delivery, leaving the other behind until the next count. With the habit of updating available and reserved together on every movement, stock tracks what's actually happening in the store, not just what was counted last time. This prevents a pile of adjustments that all need fixing at once.

You get a way to confirm stock without recounting everything

Before, to check whether stock was right, you had to recount the entire stockroom, which rarely happened. With the available-plus-reserved logic applied product by product, the store can confirm the count on one specific item whenever it needs to, without waiting for a full review. This turns checking into something that fits a normal routine, not a rare event.