If you save your feedback for a student's journal entry, but leave the grade as "no grade", then go to the "grades" view in your course, that student will have the first grade in that scale listed.

For example if I use a scale of Pass,Merit,Distinction and left it at "no grade", it would appear as "Pass".

The journal_entry database table doesn't save the grade there, that still has "0" in the rating column, it just appears to be when looking at the grades view.

Also on a similar note, if you use the 0-100 scale and leave it as no grade, it appears to assume that that default of "0" in the rating column equates to you having given it 0/100.