Hi,
Just assign G/L account for UMB key by keeping Blank for RAP key in OBYC t.code and carry out your process to find which G/L account picks!
Revaluation account triggers for material due to-->
When price change - Thee material price no longer corresponds to the current market price, you can adjust it by making a price change.
OR
A material debited / credited -if the stock value of a material is to be increased or decreased by making direct credit or debit posting for the material.
Regards,
Biju K