Currently, you can't adjust the deduction logic in OneCart for when your Shopify orders trigger a quantity deduction. In other platforms, you can pick a specific order status, and when that entire order status is received by OneCart, that's when the system will deduct the specific quantity from the SKUs in that order.

For Shopify, because you can partially fulfill an order,  but the Shopify does not reflect individual order line items as "partially fulfilled", there is a risk of "double-counting" a deduction, if you fulfill one item of an order today, and return back to it next week to fulfill the rest.

In order to avoid this, OneCart has a fixed setting so that deductions happen automatically when an order comes in from Shopify. 

If you'd like to cast your vote for this feature, please send a quick note to hello@lachmann-tech.com and we'll add you to the list as we track interest in this.