The volume shown in a ship-to's forecast is automatically pulled from that ship-to's consumption (depletion) forecast — it is not entered or edited directly on the ship-to screen itself.
Removing a SKU or Region From a Ship-To
If a ship-to is pulling in volume that shouldn't be there (for example, a planning group configured to route through the wrong distributor, surfacing units for a region you don't actually sell into), don't edit the ship-to directly — go to the consumption forecast for that customer instead and delete the row for the affected product/region.
Navigate to the consumption forecast for the relevant customer
Locate the row for the product/region you want removed
Delete the row
This will zero out the forecast columns going forward in the ship-to. Any historical actuals will remain visible in that row (since real sales occurred), but the forward-looking forecast will reflect the removal.
Exception: Customers With "Direct Order Forecasting" Enabled
The automatic consumption-to-ship-to flow described above applies to most customers, but not all. In Forecast Settings, a customer can instead be flagged as "Direct order forecasting." For these customers, the ship-to forecast is entered directly as a total shipment value and does NOT pull from the consumption forecast at all. If two similar customers behave differently, check whether "Direct order forecasting" is enabled for one of them in Forecast Settings.
Can I Manually Override the Ship-To Forecast?
Not within the Sales Forecast module. For consumption-based Planning Groups, the Ship-to tab is read-only. If you need to manually adjust a shipment number, that capability exists in the Demand Planning Module, not Sales Forecast (see "7. Adjustments, Overrides, and Collaboration").
Why a Ship-To Might Show No Volume At All
If a ship-to isn't showing any volume, check these two prerequisites before assuming something is broken:
Actualized data must exist. The Ship-to view is built from ERP shipment actuals. If no invoices have synced yet for this customer (check the "ERP Invoice Coverage" screen), there is nothing for the forecast to pull from.
The customer must be assigned as the RTM on a Planning Group. Ship-to volume is only derived for customers that are set up as the RTM (distributor) on at least one Planning Group. A new "solo" ship-to customer with no Planning Group relationship will not show any volume, even once invoices start flowing.