Field help (RVANAT) 

This field is used to enter a value for the section selected as the Nature Criterion.Group or Accounting code. This value associated with the year and potentially the month is used to identify the coefficient or index to apply during the revaluation process.
In the case of groups, only a group with the same legislation as the company or without legislation can be specified.
In the case of accounting codes, only a "Capitalization"-type code can be selected.