Looks like infusion 8 will be the Grade 2. It says I'm missing alex now for the grade two vice the wrong grade of materia and grade 1 now says wrong type of materia. The chance at success for 7th infusion on +det was 50% (one failure)
Edit: I think tier changes can be estimated (visually seen) by lookign at the glow on the scroll. It appears to be moving towards the bottom left at least for the +Det.