All my respect to Eugene Vdovin, the creator of GrossGrade program. As he said:
The current developing status is early BETA, and the author of the program is a single mortal man, so please, don’t judge severely for the unfinishings existing in this BETA or for incompletely actual documentation. In this case “BETA” stands for “beta than nothing”.
Hope someday he develop a Linux version of his program. Meanwhile we are going to continuous using other apps.