An entry using this combination is not allowed (see long text)

What causes this issue?

You have made contradictory entries regarding the determination
of values.
The possible entries are as follows:
- You want to post a complete retirement
=> Set the indicator for complete retirement, do not make any
other entries
- You want to post a partial retirement
=> Enter either the amount or the appropriate percentage
rate. If quantity updating is used for the asset, you can
also enter a quantity.
=> Enter only the quantity being retired (this is only possible if you
are not dealing with a generic retirement, and quantity
updating is used for the asset).

System Response

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

How to fix this error?

Check your entries.

Error message extract from SAP system. Copyright SAP SE.