Quantity adjustments are not allowed for buy/sell exchange &

What causes this issue?

The quantity adjustment is being made against an exchange that is
a buy / sell exchange, but no adjustments are allowed for
those types of exchanges.

System Response

Exchange number &v1& is considered a 'buy / sell' exchange agreement,
because the exchange header shows the material posting rules set to
'external'. Issues or receipts for this agreement will be invoiced as
expected. These types of exchanges are not adjusted
with LIA postings.

How to fix this error?

Enter a valid exchange number.

Error message extract from SAP system. Copyright SAP SE.