&: total of individial quantities is not same as total quantity

What causes this issue?

The sum of the individual quantities in the schedule lines for a plant
does not equal the total quantity for the plant. This can have the
following reasons:

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

The sum of the percentages in the schedule lines does not equal 100.
In calculating the schedule line quantities, the system rounded off.
The system calculates the quantities per schedule line for the total
quantitiy for a plant and rounds off to an order unit to the number of
decimal places valid for the particular order unit. Quantities are
always rounded off at schedule line level (even when order optimizing
is not selected for the rounding indicator) and guarantees that
follow-on documents are only generated with the allowed order
quantities.

How to fix this error?

You must correct the quantities or percentages for the allocation table
item to be consistent.

Error message extract from SAP system. Copyright SAP SE.