The marked standard price will be overwritten

What causes this issue?

You are attempting to <DS:GLOS.marking>mark</> a standard cost estimate
for a material. A standard cost estimate for this material has already
been marked.

System Response

In you mark this standard cost estimate, its results will be written to
the material master record as the future standard price.
The price currently shown in the material master record as the future
standard price will be overwritten.

Error message extract from SAP system. Copyright SAP SE.