If you configure Ship with FBA to the 'Auto' mode, then the app will try to ship the order via FBA as soon as it is created (or paid) on Shopify.
You can postpone the order fulfillment via FBA by specifying a delay period. After the order is created on Shopify, the app will wait for the specified delay period and only then attempt to ship via FBA.
The fulfillment delay is useful in cases where you want to wait for a few minutes for additional processing of the order, such as order risk evaluation by a third-party app.
Fulfillment delay is also useful when you want to filter (blacklist) orders for FBA based on order tags. Sometimes, you use third-party apps to add tags to the order based on certain criteria. These apps can take a few minutes to process the order and add tags. The fulfillment delay allows the Connectr app to wait for the third-party apps to add order tags before checking for the blacklisted order tags.