Field help (OSTCHGTYP) 

This zone recalls the type of credit for this BP.

If the company field is empty, i.e. there is an heterogeneous group of companies, the conversion will be done into folder currency (defined with the CURSHRFLD parameter), must be into the revised currency.
If the Company field concerns a group of homogeneous companies, the conversion will be done into company currency (defined as the revised currency or history currency according to the Credit control origin parameter.