The specifications are valid for the entire item

What causes this issue?

You have either changed the fixed quantity or date in the display for
controlling the availability check.

System Response

Since more than one order quantity exists for the item you have
processed and the results of the availability check are issued for each
order quantity, the system informs you that the change made is valid
for the overall item. This means that it is valid for all schedule
lines displayed or still to be displayed.

How to fix this error?

Confirm your change by pressing ENTER or remove the change and confirm
this with ENTER.

Error message extract from SAP system. Copyright SAP SE.