So did the LOI have a % or a $ amount? If it was a % then the financial aid office SHOULD address it because the % should be applied to the school's published COA. $ is just that; it is NOT based on a % but rather just a dollar amount. Coaches can say giving $ makes things easier but what they are really doing is reducing your scholarship on future years so they can free up $ for recruiting. I haven't heard of any colleges reducing their COA lately...
My son had an offer that guaranteed $ for four years which is exactly what I've described above. Of course the COA is expected to increase every year which means if I looked at the $ amount the first year and came up with an equivalent % I would find that this % decreases every future year. This particular school made it a little better by guaranteeing the same tuition as freshman year for all four years. So the only decrease would then be room, board, fees, and what I call "funny money" (books, travel expenses, personal expenses, etc.). "Funny money" is the amount that is not directly billed to the student.
One caveat: I'm not an expert on what the NCAA uses to determine compliance. I suppose the % could be JUST the amount directly billed to the student. In other words, tuition, room, board, and direct-billed fees. This would not include the "funny money" portion of the COA (books, travel expenses, personal expenses, etc.).