Seems like with the letter you got, they are not needing further information. They are not concerned about your grades. They want to compare you to the larger pool at regular admissions time. With the other, they are awaiting a little more information about grades. so the outcome is dependent upon the mid year grades for letter 2 whereas no further information is needed for you. So with the 2nd letter odds are dependent upon whether the candidate improved or at least stayed level.